Preparing for RavenDb v 2.5 release : "Brace yourself. RavenDb 2.5 is coming."

- Updated NuGet package and version to 0.8.
- Updated NuGet package dependencies for v2.5-unstable prelease.
- Replaced the .nupkg with .nuspec's.
NuGet spec had the core dll in the wrong location.
Created .NET 4.0 and .NET 4.5 (multi-targetting) projects.

- Changed the main code projects to .NET 4.5.
- Added two more .NET 4.0 projects which link the main code.
- Added both targeted frameworks to the NuGet specs.
- Updated the NuGet packages and version to 0.8.2.
Need a git attributes! :sunglasses: