Fixed #84, added saving and logging WebGL limit info after context creation.
Added fallback shaders, XML switch for turning off model rotation in database and polyfill for Opera support.
- added onChange property to selector component
- a fallback shader can be defined for each shader
- if only experimental context is available, alpha will be turned off
- resource center can be told to add and load fallback shaders instead of the regular ones
- shader complexity attribute added to graphics context, that can be used to turn on fallback shader loading
- the rotation of the model in the database can be turned off from XML
- polyfill added for Math.sign
- turning shadow mapping off and on made more robust
- scissor test removed
- shadow setting options are hidden when shader complexity or shadow mapping is switched down
- shaders organized into mesh and billboard folders
- simple shaders added as fallbacks