Fix sprite media location in css
Import some code from MIT App Inventor
Relax naming rules for variables and procedures

Allow anything in Blockly - the code generator deals with disallowed
characters. This also fixes the auto-naming of procedures.
Temporarily ignore warning handler
Fix variable naming in code output
Make method private
Integrate reactors into globals

- Reactors are defined as globals.
- Added another prefix for machine variables.
- Refactorered getGlobalNames so that the types of globals to select can
be chosen (you can't set a machine variable).
- Changed prefixing logic to account for extra global "types".
Fix for variable names not showing up properly