Rearrange builds by framework, other build work

- We now have solutions and project files for .NET 2.0, 3.5, 4.0, 4.5
- .NET 4.5 has an optional build config for Entity Framework 6
- .NET 2.0 uses LINQBridge for extension method and LINQ support
- Removed Visual Studio 2008 support
- Deleted monodevelop mdp/mds, mono xbuild compiles the sln/csproj
  files just fine
- NOTE: Linux/mono 3.2.1 doesn't compile .NET 2.0, LinqBridge related