Enabling admin pages in MusicStore.Spa:
- Updated attribute routing so it works now
- Created a Pages folder and PageController for serving pages, I don't
  like views very much
- Worked around an EF issue
- Fixed ApiResult to use JsonResult.ExecuteResultAsync
- Made PagedList take the sort expression so it can be conditionally applied as calling Count on the query passed causes issues if it contains an OrderBy expression
- Made web server ports not conflict with non-SPA MusicStore