major refactoring of scaffold project.

It now uses the "AssetManager" to load assets from the disk. Furthermore, it proposes a simple event-driven structure to navigate between menu and game, controlled by a "Root" class that creates the respective elements ("Game" and "Menu" instances).
updated comments
made AssetManager compatible with FDT
updated 'EmbeddedAssets' to naming conventions required by 'AssetManager'
reduced number of warnings in FDT
renamed 'media' folders to 'assets' (for consistency with code)
moved some demo/scaffold files into 'utils' package; added more methods and documentation to AssetManager
fixed ColorMatrixFilter constructor
removed obsolete filters
started with filter documentation
updated FB project after removing files
completed filter API documentation
Fix Demo source paths in Flex Builder

Use an Eclipse Workspace path variable instead of a random path on some
random developer's machine
Merge pull request #226 from threerings/demoSourcePathFix

Fix Demo source paths in Flex Builder (now using the Eclipse workspace path variable STARLING_FRAMEWORK)
updated README files of demos with information about Eclipse workspace path variable
updated scaffold README file with build information
updated FB projects and embed statements to simplify building of the demo and scaffold projects
renamed Startup-classes of demo projects (for consistency with Scaffold)
raised version to '1.3'
updated build log for 1.3 RC