Add role locking support

[sv-du]

This PR adds the ability for one to "lock" roles, thus making it that any ranking commands will refuse to rank people to that role

In case you're curious, here's what the different commands do in case of a locked rank

• For setrank, if one were to supply a locked rank ID, the command will fail
• For promote and demote, if one were to supply a locked rank ID, the command will ask the command author if they want to rank the user to the next rank available

If there are any bugs, please let me know