Add `Target.FrameworkFolder`
Add `Target.FrameworkFolder`

This allows using standard .net framework naming (e.g. net461 instead of v4_6_1) in sharpmake string placeholders. Typically we want to use these names in project and solution file names, but we cannot use the `ToFolderName()` extension in string placeholders, just properties.
ubisoftinc/Sharpmake,ubisoftinc/Sharpmake,ubisoftinc/Sharpmake