New VS2010 projects

* CSharpEx: general purpose c# extensions
* CSharpEx.Forms: WinForms related extensions
* CSharpEx.Tests: Testing library
Add InvokeIfRequiered extensions
Rename ControlExtensions class to ControlEx
Add string extensions

* SafeString
* SplitAndTrim
Create xml documentation
Add string extensions

* Right
* Left
Add xml documentation