Take the new JsDuck::Class#find_members into use.

Discard JsDuck::Class methods:

- members
- constructor_first
- members_hash
- local_members_hash
- get_members
- all_members
- reset_members_lookup!

The new #find_members replaces most of them.

Moved sorting and ordering of constructor into FullExporter,
so the #constructor_first method still exists, but is elsewhere.
Also added tests for exporter, but the export format still
remains the same.

The code for warning about statics in singleton moved to Lint.

Related to this there's one change in behavior - static members
in singleton are no more cursed into instance members.  That's
because a singleton actually can contain static members, though
it's silly and JSDuck warns about that, but you can even access
those static members in a clumsy way:

    MySingleton.statics().staticMethod();

This is where statics: {} end up when you define them in Ext 4 way
inside a singleton class.  And I've seen some classes in Ext/Touch
codebase even doing so... it's nevertheless silly.

As for the bogus @static tag use in singleton classes for members
that aren't really static - these just need to be fixed.