Stashing Katana Auth work
Started a new authentication service to pull auth-related stuff out of UserService.

Also, as a demonstration of a cleaner service layer.
Implemented AuthenticationService.AuthenticateUser
Stashing auth rearch
Moved things over to use UserSession instead of IPrincipal
Fix the DeleteAllPackageVersionsTask to 1) call DeletePackageVersionTask.ValidateArguments() which does some initialization that was missing 2) require a Reason for the deletion
Also pass through the ConfigFile and EnvironmentName arguments which DeletePackageVersionTask requires and the parent task magically gets due to the galops powershell alias.
Going with .Execute() for fuller consistency with how commands are normally invoked and easier debugging.
Moved authentication logic to its own service
Fix #1648 - error page looking wrong with no background image.
Apply Andrew's Code Review Feedback for DeleteAllPackagesVersionsTask. Untested, but should hopefully work next time someone needs to delete a package. If not, you can revert this change? :)
Merge remote-tracking branch 'ops/master' into anurse/mergemonitoring
Remove auto build numbering from build.cmd
Removed x86/x64 platforms from galops
Fixed up infrastructure
Fixes #1646 by reverting part of the fix of #1370.
Switched to default auth cookie name
Fix broken unit tests
Fixes # 1647 - erroneous message that a newer prerelease package is available. also ensures we only show this message if you are looking at the latest stable release of the package, since that is the scenario where it is most relevant.
Merge remote-tracking branch 'origin/dev-start' into dev