Greater Control of Command-TabComplete

A resubmit of a previous PR.

Allows greater control over Tab Command Complete.
You can now specify how many letters of the command must be typed before it will be tab completed this will help deter people from just spamming round all the commands to see if there is one incorrectly set up.
0 will tab complete all commands
-1 will disable tab complete

1 will mean you have to type the first letter
2 will mean you have to the second letter... etc...