Updated solution with XBehave.Net45.csproj Xbehave.Sdk.Net45.csproj and test project XBehave.Features.Net45.csproj.
Also updated rakefile.rb and some linked files to work with conditional compilation.

This is to setup the ground for issue #25
Applied feedback by changing capital letters, updating DEBUG and RELEASE targets, added missing nuget packages, etc.
Updated nuget packages version, build actions, after build events, capital letters, etc.
Updated reference to XBehave project from Xbehave.Features.Net45.csproj
switched to absolute paths for xunit runner params
Merge pull request #125 from adamralph/net45

Added NET 4.5 projects