Port System.Runtime.Caching to .NET Core (dotnet/corefx#24756)
* initial System.Runtime.Caching project check in
* Initial check in of System.Runtime.Cachine code
Including updated project file with missing dependency on System.Private.CoreLib
* S.R.Caching src and ref
- addressed the PR review commends
- added ref cs and csproj files
* Fix NETFX build
* Fix configs
* Adding resources
and addressing PR feedback
Commit migrated from https://github.com/dotnet/corefx/commit/
2e1f9fc09800515a41e03431470a3c04133c814b