[Mono-osx] ButtonMaddness new sample

[Pavel Sich]

On http://github.com/sichy/monomac/

there is a new code for the ButtonMaddness sample with added 
functionality (mainly event handling). I have used code from today 
afternoon to work above it. I have added other more Cocoa API bindings 
as well, in the SRC\AppKit subfolder there are new files added:
NSLevelIndicator.cs
NSSegmentedControl.cs

with property Cell override and NSSegmentControl has 
UnselectAllSegments() method added for easier manipulation. Btw. it is a 
really nice concept having the generated code with the g.cs as suffix 
and availability to add own partial implementation, that allows such 
tweaks, great work guys.

Also do not forget to update the makefile to include the newly added 
files in AppKit to be compiled.

Cheers,
Pavel
@sichy

P.S. I will pick another sample from the mac dev samples and will work 
on it. Something with the table would be useful I guess.