Clear out inbox option

Fixes Inboxen/website#167
Add option for Inbox to be disabled

This will allow users to disable an inbox for a period of time, but won't delete emails already received

Fixes #7
Allow users to view disabled inboxes - we're not deleting emails when the Inbox is marked as disabled
Actually set disabled flag from form ☺
Create a subform for "dangerous" Inbox options

Part of #19
Only link to delete inbox form from edit page

Now the user will see the delete button when they go to edit the inbox, rather than having a separate page

Fixes #19
Change up breadcrumbs to reflect how user got to delete page

Also, don't separate "Edit" and inbox address in breadcrumbs
Create a proper style class for disabled inboxes

Disabled inboxes now only display the "disabled" label

This also required us to up the opacity of "close" class links - I thought they were too light anyway
Merge branch 'clear-inboxes'