maccore: add as a submodule
Makefile: update clean target
run update-docs
NSTextAttachmentCell: add NSImage ctor, allow instantiating

There were two methods marked [Abstract] which was incorrect.
As such the whole NSTextAttachmentCell class was generated
as abstract, meaning it was only usable if subclassed, which
is not the case in Objective-C. As in Objective-C, the following
is now supported: new NSTextAttachmentCell (new NSImage (...))
maccore: add as a submodule
Makefile: update clean target
run update-docs
Fix broken build when build system only has Xamarin Studio installed and not Monodevelop
Fix return type of NSTreeNode representedObject - should be NSObject, not NSTreeNode
NSTreeController.Content property should be NSObject, not NSTreeController

See https://bugzilla.xamarin.com/show_bug.cgi?id=13792
Update docs for CFType refactor in maccore
Add bindings for IOKit for accessing USB.
Track MacCore changes
Track MacCore changes for moving Mach
Track MacCore changes for adding IOHID bindings
IOKit docs
CoreBluetooth bindings
IOBluetooth bindings
IOBluetoothUI bindings
fix docs Makefile