johani tweaks

[johanix]

• manage error return in missing places in FSM engine / engines
• clean up another set of old SQL prepared statements that we don't need or want
• had to add new methods to *MusicDB: Query() and Exec() which is ugly and unfortunate. Should look for better way of doing that (but it is no worse than what we had, and getting rid of the prep statements was the goal here).

[johanix]

Happiness is a negative diff.