Added missing file headers.
* Fixed a lot of StyleCop and FxCop issues.
* Added the Contracts namespace to provide argument checking capabilities similar to code contracts.
* Added new extension methods for bool, enumerables, StringBuilder, and Type.
* Added additional extension methods for DateTime, numerics, and string.
* Refactored a lot of the extension methods to make use of the new Requires class.
* Moved the extension methods into an Extensions namespace.
* Added a generic EventArgs{T} class to simplify creating EventArgs derived classes with a single data value.
* Added an extended IDisposable interface called IDisposablePattern that adds a Disposed property.