First cut at experimental plc reference resolution
Tweaked the references formatting
Patched up the correct paths for IsValid type project references
Added comments
Cleaned up unnecessary code due to earlier bug with FSharp.Core being blocked by the loader
Removed code remapping msbuild path this is not necessary
Used the presence of ".NETPortable" directory to resolve portable folder location
Remove hard coded directory name using TargetFramework constants instead

Changed logic so that project references are always returned even if
portable references are not found at the requested location.
Fixed refactoring typo
Drop toArray, not needed
Merge pull request #521 from 7sharp9/pcl

Pcl initial work