Check for internal extension before fixing URL

Only internal extensions need their URLs fixed. We should probably find
a better way to do this, but it's tricky if we want the offline editor
to be able to load internal extensions without an Internet connection.
Merge pull request #425 from LLK/fix-url-fixing

Check for internal extension before fixing URL
Fix whitespace in ui.ProcedureSpecEditor
Rename duplicate parameters in procedure editor