Cleanup: use env_path instead of building the path
Display unit context as well
Docs: improve examples for update_code Fabric command
Change the latest activity message shown inside a TP

Now the message:

* is shown after the folder stats inside a box,
* includes an italiziced snippet from the unit source (or target), if
  applicable,
* the snippet shown might be trimmed to 40 chars, appending an ellipsis if
  trimmed.

Fixes bug 2964
Fix mysql root escalation

The --defaults-group-suffix=_root option has to precede any options
that take separate arguments (like "-u root").
This is true for mysql and mysqldump.
Also, add root escalation for dump_db and load_db commands.
Note exception to MySQL db root escalation
Don't fail fast for unstage_feature
Never put sudo and rm -r together
Clean up POOTLE_EXPORT files created by staging server activity
Comment out (and fix) Firefox copying

It wasn't doing anything except copying the files before, but there are
other issues, better to comment it out now that it actually creates the
project in the DB models.