RecordingForm: remove preview player widget

Can still launch external player to listen to file
QualityWidget: add a new custom Quality widget

Use it in the RecordingForm
Close Adapter when App quits

Prevents a warning message on the console.
MainWindow: make repository a construct argument
Move 'import' functionality to Repository

Also 'database-changed' signal
Add 'audio-path' constructor arg to Repostitory

This is required to move the file import functionality to Repository
instead of Application
Re-organize main window and create WelcomeScreen

Move the list of recordings into a separate widget placed in the
'Recordings' tab, and offer several other tabs (for "locations", etc)
Show list of locations in the 'Locations' tab