Fixed control/tab bar label shadows

NSShadowAttributeName has no effect when using CTFrame. Use
CGContextSetShadowWithColor instead.
Fixed occasional “too light” title bar gradient

This would mainly happen when creating new windows with a file browser.

Described at:
http://stackoverflow.com/questions/5812593/nswindow-textured-gradient-fill-weirdness
http://stackoverflow.com/questions/7795505/nswindow-textured-background-with-nstextfield/11482772#11482772
SymbolChooser references OakDocumentView instead document

Since a document cannot send notifications, this will allow the
SymbolChooser to monitor and respond to notifications from the
DocumentView.
SymbolChooser live-updates its selections

This code is public domain.

Closes #166.
Rework symbol chooser code

The symbol chooser is now owned by DocumentView instead of DocumentController.

The symbol chooser does not know about its owner and is not an observer of any notifications. Instead it has a property for “document” and one for “selectionString”. It is the owners job to update these properties (i.e. when switching document or changing the selection).
Fix crash when pasting in file browser

This started after upgrading to clang-425.0.24. More info at https://github.com/sorbits/rdar/tree/master/for-in-with-ARC