Move the local music view into a user control

The tag editor doesn't work yet, we move that activation logic later
Moved the Youtube view into a user control
Move the SoundCloud view into a user control
Removed unused code
Move design time things into their own namespace
Move the artists and the song detail views into their own user controls
Fixed a binding path
Removed unused using and useless comments
Re-activate the tag editor
Simplify expression
Merge pull request #130 from flagbug/refactor-shellview

Refactored the ShellView