Added ExtCore Nuget Package
Added FSharpActivePatternCase Xml Documentation
Remove namespace prefixes
Add LRU based cache for XmlFile with a  limit of 20 in cache

Remove some dependence on the util module in FSharp.CompilerBinding
which is copied from VFSPT and ExtCore, use ExtCore direct.
Remove dependency on AsyncMaybe in util.fs in favour of ExtCore
Make Utils internal to stop external use as we try to depreciate use of CompilerBinding
Add ExtCore open instead of copied code
Add ExtCore open instead of copied code

Refactor out Option.getOrElse which was in Util.fs
Add ExtCore open instead of copied code
Add ExtCore open instead of copied code
Add ExtCore open instead of copied code

Add Option module with tryCast ass we use this in several places, Ive
asked Jack Pappas if we can get this in ExtCore
Add ExtCore open instead of copied code

Factored out getOrElse
Add ExtCore open instead of copied code
Merge pull request #743 from 7sharp9/cleanupWithExtCore

First round of cleanup with ExtCore