Various changes to plug-ins (Allow scripts to use all squirrel libs, etc.)

- Load the blob, io, and system squirrel libraries for scripts
- Removed the "command" setting associated with plug-ins,  The interface
for the "fe.plugin_command()" functions change as a result
- Added "fe.load_module()" script function
- The "Toggle Layout" action will now just toggle between layout scripts
beginning with "layout" in their name... so between "layout.nut" and
"layout.90.nut" for example
Issue #59 - added jump to previous/next letter controls