There needs to be a separate mechanism for giving people access to
all the assets used in documentation.  The previous approach of
writing out guides/videos/examples JSON files generated needless
files for most users of the docs, while not really helping the
people who wanted the actual source files of the docs, as these
files weren't really the actual source files, only gone-through-jsduck
versions of only some of them.

The default icon files is now icon.png.  When guide doesn't contain
it, icon-lg.png is looked for.  When that is also missing, the
default guide icon is used.

This was a hack with no obvious need.

All guides are now read only from guides/ dir, like in ye old times.

When used on a member, it's treated as if the doc-comment wasn't even
there.

When used on a class, all its members will be ignored too.

This makes it a useful tool to easily exclude a class or a member from docs.

Singletons and components are now shown with their designated icons
in search results dropdown.

By default MetaTagRegistry.instance will return a registry that's
loaded with builtin tags.  This instance can be overridden for
testing and for loading custom tags.

This greatly simplifies tests and makes them faster as we no more
need to ensure that MetaTagRegistry has been loaded with builtins
before running the tests.  The registry is only instanciated once
for the general case and second time for running special tests
against itself.  Previously initialization happened multiple times.

Hacks no more needed to inject private tag into meta tags list,
it's now in there naturally. Although now I'm doing a small hack
to make :private appear on doc object hash itself.

With this, the [pri] label will appear in search results dropdown.

This way one can easily differenciate between static, deprecated, and
other types of items in search results.

It's now OK for a guide to be listed in multiple groupes, but when
it's listed multiple times within one group, a warning is printed.

Also added new warning type :dup_asset.

Build a map by position type once, instead of filtering tags list every time.

Previusly null resulted in type=nil which caused problems when
@cfg happened to be @accessor that generated methods which then
ended up having nil return type and nil param type.

@hide is no more equivalent of @private.  Members tagged with @hide
won't appear in documentation at all.

This variable is no more used.

Simply use the same icons that the actual guides/videos/examples use
and force-scale them down to 50px width.

Also output file and linenr when context available.

Previously these fields were named "text" and "desc" which was
different from guides and videos for no actual reason.

We still support the old field names for backwards compatibility.

For now using the same icons as in tabs.

The tags can now position their content either above or below the
other content, while defaulting to placing it below like all tags
were before.

Using the newly aquired ability to access assets in to_html method.

At the moment this changes nothing, as currently examples have no
names assigned and so the "url" field will be assigned to "name" field.
But it opens up the opportunity of assigning names to examples if
needed.

More importantly it makes the handling of examples more similar to
guides and videos.

For this create a base class GroupedAsset that deals with
building the map of names.  To make the base class work, all
classes now use @groups instead of @examples/@videos/@guides
so they can be treated the same in GroupedAsset class.

The base class also has #each_item method to more easily iterate
over items in all groups.

For examples we are now also creating the "name" field into all
of its items.

With this ready, our @aside tag can start accessing guides, videos
and examples.

Assets combines: guides, videos, examples, images, welcome, categores.

This moves out bunch of logic from App class and simplifies
communication with IndexHtml and AppData which now only need to get
passed one param, instead of passing guides, videos, etc separately.

Video URL-s are now much friendlier.

When video only has an ID, turn the ID into a name (for backwards
compatibility).

Additionally I built a duplicate name checking into the processor
of videos.json, which right away discovered two duplicate videos :)

Use it for global classes Array,Date,etc and for Ext.supports.

For now this is hard-coded, but better than nothing.

Replace the .forEach with for-loop.

Didn't really measure the benefit, but maybe something goes better in
IE, as it's a heavily used loop when performing the search.

Also style them with -line-through-.

That is, don't complain when a deprecated member is missing
(this is to be expected).

An extra checkbox in show menu, just like for deprecated.

Otherwise like @deprecated, but for documenting members that have
been completely removed.