added special handling for system and tiddlyspace bags in groupBy plugin.
added special handling for system and tiddlyspace bags in groupBy plugin.

In TiddlySpace there is a system space and a tiddlyspace space. These are separate
from the tiddlyspace and system bags.

Now tiddler from the system space will be grouped under system whilst tiddlers
from the bag system will be grouped under *system.

TiddlySpace/tiddlyspace,FND/tiddlyspace,FND/tiddlyspace,TiddlySpace/tiddlyspace,FND/tiddlyspace,TiddlySpace/tiddlyspace