Allow user to change its own Quassel password

Summary:
Quassel doesn't currently offer a mechanism to let users to change
their own passwords.

But it offers a maintenance script for administrators, and Quassel users
have an account on Eglide so a solution is a sudo wrapper to allow it.

Usage: chquasselpasswd

Ref T1384

Test Plan: chquasselpasswd

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1384

Differential Revision: https://devcentral.nasqueron.org/D1532