* Add `disallowedwords` setting and perform check
Check if any of the words in `disallowedwords` are contained in the username. If
so, return false like other checks.
NOTE: Needs testing for advanced bugs.
* Remove "administrator" from `disallowedwords`
"administrator" contains "admin" anyway, so it is not needed.
* Add error message if username contains a disallowed word
* Add `disallowedregexp` setting and perform check
Check if each expression in `disallowedregexp` exactly matches the username. If
so, return false.
TODO: Add specific error to dialog in `window_main.cpp`.
* Add error message for username matching RegExp
* Fix indentation
* Compile `disallowedregexp` into a QList upon initialization
Reduces system load with each registration request.
* Clean up `isUsernameValid` function
* Fix indentation
* Add backwards compatibility to client
Client can accept either 7 or 9 rules to maintain compatibility with older
versions of server.
* Add examples and warnings to `servatrice.ini`
