Merge pull request #2732 from radical/asm_remap

Do not remap framework assembly if it's version is higher than the ru…

…ntime version

Currently, assemblies like Microsoft.Build.Framework and
Microsoft.Build.Engine get remapped to the current runtime version, at
load time. This means that if an assembly references the above
assemblies with a version like `14.1.0.0`, then that would get remapped
to `4.0.0.0`. This is incorrect behavior and breaks msbuild. Instead,
now we do the remapping only if the requested version is lower than the
runtime version.