Allow administrator to change user password in control panel

[joeholdcroft]

Feature description

Currently an administrator must log in as an user and go to the account section to change the user's password.

We should provide a form where they can change the password directly from the control panel. We may want a new access level for this? Related to #16.

We should also ensure there is a confirmation input to ensure the password is entered correctly.

Related Issues / Trello Card / Code?

Uniform Wares wanted to know how to change a user's password: https://trello.com/c/xHsfjdL8/501-a-retailer-has-changed-the-password-for-the-retailer-login-it-needs-resetting

Anything else to add? (Screenshots, background context, etc)