Added unittests for EntityComponentSystem<...> and IComponent<T>
Added the files to the xbox and windows phone solutions

Added:
MissingEntityTemplateException.cs
EntityComponentProcessingSystem.cs
Extensions.cs
Added comments to EntityComponentProcessingSystem.cs
Added comments to MissingEntityTemplateException.cs
Merge branch 'master' of github.com:Marwes/artemis_CSharp
Reverted changes that was accidentally in the master branch

This reverts commit 1177195ed2252ebf3463e7ce7ac65055c6f39bd7.