[TxMt] request for a $TM_BUNDLE_PATH

[Jan Sabbe]

I would like to have a $TM_BUNDLE_PATH available in a command, that 
points to the directory in which the current command is stored. For 
example, $TM_BUNDLE_PATH would point to 
/Applications/TextMate.app/Contents/SharedSupport/Bundles/HTML.tmbundle 
for the Refresh Safari command.

This would make it easier to make more complex commands (just let your 
command execute $TM_BUNDLE_PATH/my_fancy_script.sh) or pack in some 
extra resources.