Disable experimental features iff we're on a stable branch.

Current experimental features are:

- The GUI
- The `upgrade` command.

This also gives us the version number on the help screen, and flips a
previous custom exception to a kraken.
Merge remote-tracking branch 'origin/release-v1.0' into disable_experimental

* origin/release-v1.0:
  CmdLine: No longer spam the user with file removes
  Force a GameData scan after installing mods.
  NetAsyncDownloader: Throw MissingCertificateKraken on missing certs.
  Cmdline: Fix typo: "Manage KSP insatlls".
  No longer query the user during transactions.

Conflicts:
	CKAN/CKAN/Types/Kraken.cs
Merge pull request #337 from pjf/disable_experimental

Disable experimental features iff we're on a stable branch.