Implemented 'Convert if statement to ?? expression' action and tests.
Added pattern matching to convert if to null coalescing action
Changed ConvertIfToNullCoalescingAction to use match.Get<T> instead of (T)match.Get or match.Get as T.
ConvertIfToNullCoalescingAction: Removed method to remove parenthesis, since pattern matching made it obsolete.
Merge branch 'master' of github.com:icsharpcode/NRefactory into luiscubal-if-to-null-coalescence

Conflicts:
	ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj
Merge pull request #203 from mono-soc-2013/luiscubal-if-to-null-coalescence

New ConvertIfToNullCoalescingAction