Correct fail load debug assembly

Correct fail to load assembly GitTfs.Vs11.dll in debug and GitTfs.Vs2008.dll in debug and release.

I think no one use TFS2008 because that should not work...

Error thrown : "Could not load file or assembly 'GitTFs.Vs11.dll' or one of its dependencies. An attempt was made to load a program with an incorrect format."