Fix #298 - Added ModelMetadata.Container property and unit tests.
Merge branch 'Fix298' into dev
Delete trailing whitespace
- #EngineeringDay
- Total replaced: 660  Matching files: 270 in *.cs
- Total replaced: 250  Matching files: 32 in all other files
- Total replaced: 22  Matching files: 8 in a few stragglers

Did not change files under following directories
- test\Microsoft.AspNet.Mvc.Razor.Host.Test\TestFiles\Output
- test\Microsoft.AspNet.Mvc.FunctionalTests\compiler\resources
- test\WebSites\TagHelpersWebSite
(Razor generates trailing whitespace in a case or two)
[Fixes issue #1528] default reference assemblies made extensible
- Made ReferenceAssemblies and GetCandidateLibraries virtual
- Added relevant tests