Now uses regex.
Added "."
Updated login message

Can now only be made up of [a-z][A-Z][0-9][-_]

QSqlQuery already executes not-empty queries, no need to call exec()

+ Added the ability to see the account age of registered users. Changes
are both in server and client. The server will now send back the
registration date along with the user data. The client will then use
this to calculate the account age and display it in the user details
window.

Specifically this should cover people connecting with a username of
"\u200C"