Switched to GlobalAssemblyInfo.cs for AssemblyVersion attributes.

I submitted a pull request for the equivalent thing in ServiceStack.OrmLite, after noticing that not every DLL was getting the proper 3.9.43 version in this latest release. (Some showed 1.0.0.0, like ServiceStack.ServiceInterface.dll.)

Lacking the appropriate VS project types, I did not modify the Android, WP, or SL projects, but all projects in ServiceStack.sln have been adjusted to use this mechanism. The others could be modified by someone else, or by manually editing the .csproj files to add the three-line reference to GlobalAssemblyInfo.cs.