This cli does:

1) Install / update langpacks by listing the languages by their code,
   eg de = German, fr = French like so

sudo -u www-data php admin/cli/sync_langpacks.php -l=de,fr

This will make a backup of the existing language (if exists) into the
dataroot langpacks_backup directory.

2) If you don't want to make backups then add the -b=false flag, eg

sudo -u www-data php admin/cli/sync_langpacks.php -l=de,fr -b=false

3) If you need to rollback the backups you can use the -r=true flag, eg

sudo -u www-data php admin/cli/sync_langpacks.php -l=de,fr -r=true

It will ignore trying to update the 'en' language as that is set
within the Mahara system itself

behatnotneeded

Change-Id: I4ec773126cc45a87fc78dec658e97856eec05338
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>