Fixes:

 * Restore widgets.py
 * Fix imports for local files
 * App can be stpped with Ctrl-C
 * Updated gitignore
Add signals import
Fix imports
Set data folder for resources
Fix 'gtk_application_prefer_dark_theme' property read
Set callbacks correctly
Use correct name for headerbar.ui
toolbar: correct stackSwitcher variable name
Correct variable name for self.toolbar.headerBar
Correct variable name for selectionToolbar
Update SONGS_COUNT name
Make useStack be optional, call __init__ with self
Merge pull request #18 from roignac/master

Fixes