Issue 6559: Command Line is broken after disabling and enabling Firebug

https://code.google.com/p/fbug/issues/detail?id=6559
Propagate errors in user command handlers similarly to other handlers
Remove some dead code
Added comment to checkFirebugVersion()
Extend the logic for safe function calls a bit

E.g. "getEventListeners(window)." should auto-complete.
Issue 6522: Implement the getEventListeners command line API

http://code.google.com/p/fbug/issues/detail?id=6522
FBTest for issue 6522 (Implement the getEventListeners command line API)
Removed some more dead code based on Firefox version comparison
Move net/176 to a new subfolder 'filter'
Remove txt extension from 'mimeExtensionMap' and prefere the mime type in such case. This also fixes net/filter/176 test
Merge branch 'master' of github.com:firebug/firebug
FBTest fix paths
FBTest: test for issue 6474
FBTest for issue 6530
Merge branch 'master' of github.com:firebug/firebug
New tracing for start-up exception
Issue 6541 (Hovering an element inside Selectors side panel scrolls it
to the top)
http://code.google.com/p/fbug/issues/detail?id=6541
Merge branch 'master' of https://github.com/firebug/firebug.git
Removed one more dead code related to Firefox version check
Avoid on* attribute being set using setAttribute (related to issue 5768