Percentage strings for width/height
Allow whitespace in percentage strings
Add method for defining default style for a class

See samples/sample56.rb for a test
Change order so percent strings also flow through relative calculations
Clearer handling of invalid strings
Create SWT backend for Download

This allows us to push off the processing of the Download's block
to the GUI thread to avoid thread access errors.
Fix failure in SWT test

Highly suspect this isn't the right way to address this, but found that
the async_exec wasn't being called properly in the spec running. No idea why not.
Merge branch 'percentage_widths' of git://github.com/jasonrclark/shoes4 into jason/percentStrings
removed global variable access in favor of #match
Merge branch 'fix_for_download_thread_access' of git://github.com/jasonrclark/shoes4 into jason/download_fix
just spec that eval_block is an outgoing message
Merge pull request #460 from shoes/style-for-elements

Implement style method for default text block styles
prepending is handled in SlotContents now
Stop including the DSL module into Slots

* everything is executed within the app context
* introduces Clear module, since that's remaining as a common bit
  of functionality, looking to kill it somewhen though
* Significantly reduces amount of specs run since all the DSL
  specs don't have to be executed for Stack/Flow
hover/leave are defined to be defined for individual slots
Better naming and dryer mouse control listener additions
in_bounds? fix taking into account absolute positions not relative ones
Added a few specs to increase test coverage
removed the repeated app.stubs
Moved general specs over from dsl_spec to the DSL specs

* we run all the specs under spec/shoes/ with every backend
  e.g. mock and SWT so they work for both
* the specs I left in dsl_spec are SWT specific due to the
  add_painter asserties which is an SWT thing