Allow user availability fields to be updated via wsuser form for testing

Add form elements to the /admin/user/wsuser page, and a submit handler, to
update a user's availability fields when testing, because the 'Edit Profile'
page automatically updates some fields to either 0 or the current
time when saving. RE: Pull Request  #364
Add testing capability to reminder function, and form/handler to run tests.

Modify the function that queues reminders/pester emails for unavailable
users to allow for easier testing. Add form elements on the /admin/user/wsuser
page, and a submit handler, to run the tests. Info on users that would
receive reminder emails is displayed in the message area, and actual
emails are sent to the specified test email address. RE: Pull Request  #364