First spike for MVC5 support

First spike for MVC5 support
* Added NuGet package manifest
* Added compiler constants
* Added NuGet dependencies
Updated MVC5 package dependencies
Added sample application
Updated build script for MVC5
Explicitly running NuGet package restore from build script
Removed dependencies on old prerelease packages
Added initial MVC5 sample application
Fixed Autofac module dependency
Merge branch 'feature-204-mvc5' of github.com:maartenba/MvcSiteMapProvider into feature-204-mvc5
Updated MvcSiteMapProvider.csproj to reference MVC 5 libraries in the correct packages directory (without specifying rc1).
Updated projects files to standardize on TargetFramework v4.0 again
Created MVC5-specific solution file and updated sample app
Merge pull request #243 from maartenba/feature-204-mvc5

Merge MVC5 branch into master
Fixed typo in comment that was causing XML validation errors in Mvc.sitemap of the MVC 5 test project.
Modified MvcSiteMapProvider (legacy) package description to be more clear that all that is needed to remove it is to downgrade the one package, not all of them.
Update README.md
Downgraded MvcSiteMapProvider.Tests project to use MVC 4 because NUnit doesn't work with MVC 5 for some reason. Upgraded NUnit to 4.3.0.
Merge branch 'master' of github.com:maartenba/MvcSiteMapProvider