BREAKING CHANGE: Remove support for Claims Principal Extensions (#144)

These extensions have the potential to lead people astray - and methods
like`GetRoles` can be misleading because a `ClaimsIdentity` already
stores on itself which claim type represents roles, but this is
hardcoding a specific string.

Author: BenjaminMichaelis

IntelliTect.Multitool.Tests/ClaimsPrincipalExtensionsTests.cs

@@ -52,12 +52,6 @@
   string fullPathToTheFile = Path.Combine(IntelliTect.Multitool.RepositoryPaths.GetDefaultRepoRoot(), "TheFile.txt");
   ```
 
-## Security
-
-- ClaimsPrincipalExtensions: Extension methods to get a user ID and roles.
-  - `GetUserId`
-  - `GetRoles`
-
 ## Extensions
 
 - StringExtensions: Extension methods for `System.String`