Email Aggregation

Rather than sending out an e-mail per activity, mails will be aggregated with other emails that have ocurred recently.

This work adds an `emailPreference` field for each user where they can select how they want their email delivered.
 * Never
 * Daily
 * Immediate (with a 10 minute delay to let it aggregate with other activities in those 10 minutes)

The emails are now also internationalizable by virtue of re-using the 3akai-ux template macro's and UI bundles.
Push out email based on the user's timezone
(Issue 858) Do not create Etherpad table from Hilary as the etherpad driver does that
(Issue 858) Configure Etherpad to talk to Cassandra in TravisCI
(Issue 858) Shoo away crummy cats
(Issue 858) Changing etherpad keyspace to 'etherpad' instead of 'oae'
add a test for user asking for a language we don't support
Store principal profile pictures in new directory
Add ability to get permanent signed download url
Merge pull request #871 from stuartf/locale-tests

add a test for user asking for a language we don't support
simplify runPagedQuery

removed workaround for fixed cassandra issue
add a test for anon users that speak multiple unsupported languages
remove calls to shelljs from previewprocessor
add meaningful error message
fix recursive cleanup
make comment more clear about what is being tested
Adjusted test docs
use cassandra 1.2.16 on travis
clean up test comment
Merge branch 'simplifyRunPagedQuery' of https://github.com/stuartf/Hilary into simplifyRunPagedQuery