Tidy up favourite scanning

Transmit no longer stores favourites in the prefs file, but in an sqlite file. The easiest way of accessing favs is now with SB/AS, but this has the penalty of having to launch Transmit, so its effects have been kept to a minimum
When connecting to a favourite, don't open a new window if there's an empty one already open
Make the 'mount as disk' action an alternative to the 'connect' action
Merge pull request #2 from quicksilver/pjr

Tidy up favourite scanning