Add detail and clarifications to syncdb/migrate
Add Fabric commands drop_db and upgrade
Fabric update_db fixes

_migrate_fake for initial `migrate --fake 0001` for 2.5->2.5.1 conversion
(but only if it is still needed!)

Eliminate extra settings(hide(...)) unneeded for setup_db/update_db
Documentation cleanup for deploy README.rst
Add working version of update_staging script

Apart from being an example of copying one deployment to another, this also
provides an example of using Fabric commands for performing a Pootle upgrade.
Enable Firefox project setup for update_staging

Also create debug UI languages
Copy Pootle PODIRECTORY too

[ci skip]
Add workaround for Connection Refused exceptions

When performing a number of ssh commands in quick succession with Fabric
some sort of rate limiting is kicking in; causing following commands to
get Connection Refused errors.  Sticking a few sleeps here and there seems
to help.
Add warning about --fake