Fixes #125 - Avoid double-prompting on initial login

Previously if prompt=login was passed for the authorize request and the
end user was not currently authenticated with IdSrv3 they would be asked
for a username and password, twice, before being redirected back to the
client.

Now they will only be challenged once, in both the 'user is currently
authenticated' and the 'user is not current authenticated' cases.
Added note on signature format
Fixed a documentation bug
Reformatting
Updated EndpointSettings
Add new DataProtection code prototype
Replace old JWT message protection with IDataProtector
Merge pull request #126 from ciaranj/fix_initial_prompt

Fixes #125 - Avoid double-prompting on initial login
Silly renaming exercise
Added license headers
Removed old protection mechanism
More code to be removed
Updated SelfHost with new Nuget
Added DH.Logging
Added Diagnostics.Trace logger
Added some test logging to ws-fed controller
Switched all logging code to new logger
Updated logger classes
Changed logger name
Merge pull request #137 from thinktecture/New_Logging_Framework

New logging framework