Install librocket deps for examples (on WindowsOS)
Introduce Size2 division operator
Fix disabling of OSX fullscreen spaces

This must be done before the call to nom::init -- or
nom::init_third_party when not using nom::init -- as the hint
internally depends on SDL's video subsystem to first be initialized.
SDL_helpers: Introduce ::available_render_driver
Use nom::available_render_driver in app ex && libRocket tests
Finish support for SDL2 independent resolution scale

* ttcards.rcss: Declare a default datagridheader tag for font style
used.

* UIContext: Introduce ::debugger_size, ::set_debugger_position; these
are necessary for correctly positioning the visual debugger, relative
to the resolution scale in use.

* libRocketDataGridTest: Use testing resolution of 768x448 && update
style sheets to better match the coordinates used in TTcards.
DecoratorFinalFantasyFrame: Fix out of bounds rendering bug

Account for negative dimensions, otherwise this can lock up the
rendering loop...
InputStateMapper: Ignore key repeat logic unless non-zero (explicit)

This logic change means that by default, keyboard input actions are
triggered whether or not they are marked 'repeating' by the underlying
events subsystem. Otherwise, holding down a key would (by default) only
trigger once, unless explicitly mapped with a key repeat value of one.
UIContext: Fix offscreen display of err beacon

Add rudimentary support for using err beacon with SDL2's independent
resolution scale.
Refactor positioning & size methods of UIWidget && friends

UIWidget and friends now all use a void default constructor and
needs an explicit call to ::set_position and ::set_size when
necessary. This is to cleanly support the use of setting RCSS
properties directly in the stylesheet / RML document.
  Ultimately, this simplifies the code-base.

UIWidget: Remove inheritance of Transformable.
UIWidget: Rename set_document_file to load_document_file.
UIWidget: Remove ::initialize; this is replaced with the existing
::show method.

UIWidget: Introduce getters & setters for position & size; these
operate on the body tag position and size -- was using body.window
before.
UIContextEventHandler: Minor clean up of code
Improve CardsDataSource & DataGrid tests

The overall performance of CardsDataSource -- loading, paging stutter
and consistency of FPS -- has been improved by a factor of two by
updating only the row offsets that are necessary within the applicable
methods (::set_page, ::insert_card, etc).

* dataview.rml: Break up 'card' col field into three; 'available',
'id', 'name'. This allows for much better management; use 'available'
for marking of card text gray when applicable (goodbye ::on_rowupdate
in the test).

* CardsDataSource: Add support for partial pages; this allows us to
arbitrarily insert & remove cards at will, with automatic refreshing
of the internal rows -- with respect to a customizable number of cards
per page.

* libRocketDataGridTest: Remove on_mousescroll event listener &
function.
* libRocketDataGridTest: Use on_keydown only for paging functionality.
* libRocketDataGridTest: Finish implementing proper multi-card
selection.
* libRocketDataGridTest: Introduce synthesized events for
UIDataViewList test; these aid automating a large portion of this
overall test case.