Member icons are now defined in member tag classes.  There the
:icon field defines the icon file which is included to the docs
app resources and an appropriate CSS gets generated.

In Ruby 1.8 it happens that MemberTag is loaded twice and the
constants in it get redefined, and trigger a warning.

A bunch of these were used in the old Touch welcome page, which
no more exists.

Some were leftovers from various style changes throughout the
Docs app history.

Instead use the already defined :tagname field.

Was forgotten in at previous refactor.

Plus a typo.

With this we completely get rid of the @merge_context variable,
and all the merging happens in Tag::Class or MemberTag subclasses.

A bit of a duplicated code in Cfg and Property, but we get rid of
the explicit check for :cfg/:property/:css_var in Type class.

This contains a fix for the changed newline handling in IE10.

Fixes: #373

Only use the :method category in @merge_context.

So no more does one need to choose between two types when creating
his own member type.

The only problem at the moment is that I needed to add explicit check
for :cfg/:property/:css_var to Tag::Type#merge.

Add :default and :optional config options and only return these
fields when these configs present.  With this we now also allow
the syntax for default values without the optionality-braces:

    @mytag {Type} name=<some funky default value>

Added a separate testsuite and updated all calls to
Scanner#standard_tag().

Related to: #374

Previously there were installation problems with therubyracer 0.11.x,
especially in OSX. But these are now gone with later versions of
therubyracer, so we can safely remove this restriction from JSDuck
dependencies.

Fixes: #371

Calculate exp and var locally as needed.

Do the proper_function? detection just once.

Do all the method-data detection inside it.

Significantly improve readability.

This class really only deals with detecting the return type - so
the old name was not precise enough.

The URL gets now returned by the search server in correct format.

But this time instead of re-running the search every time we
need to navigate to a new page, just remember the search results
and only render the page.