In staff type dlg box, only displays staff types from groups relevant to staff instrument.

Also removes the default guitar string data, which does not make sense for non-stringed instruments (stringed instruments are assumed to have proper string data in instruments.xml anyway)
Add comments
Fix tab order and buddies of staff type dlg box
Renamed stafftype.ui to editstafftype.ui
Apply template filtering to instrument wizard too.

Also fix selection of current template in instrument type combo box.
Fix build error.
Fix tests (maybe...)
More test fixes...
Fix crash when adding to the Instrument wizard a new instrument without an associated preset.
Merge pull request #907 from mgavioli/relevant_staff_types

Staff type dlg box: Relevant staff templates only