Added app trending calculations (bugs 911275, 911280)

This adds a table to store trending and per-region trending and a cron
to update this trending table.
Added ES settings for test runs
Commit from Mozilla Verbatim by user michael.koehler1@gmx.de.: 5474 of 5474 strings translated (0 fuzzy).
Localized a few more strings for el
Merge pull request #1105 from alexmiog/alexmiog_el

Localized a few more strings for el
Add limit to the number of Collections returned for featured search endpoint (bug 910311)
Disable fallback for featured apps collections in search/featured (bug 910311)
Testing the presence of the bango-portal switch (rel 898085 PR#1096)
Merge pull request #1106 from davidbgk/898085-bango-portal-link

Testing the presence of the bango-portal switch (rel 898085 PR#1096)
fix packaged app reviews (bug 913431)
fix packaged app rating tests (bug 913431)
handle repeat postbacks (bug 860118)
Merge pull request #1108 from wraithan/repeat_postback

stab at handling repeat postbacks (don't merge) (bug 860118)
Implement the full fallback mechanism for filtering collections (bug 910311)
Merge pull request #1102 from diox/collections-featured-apps-limit

Improve filter fallback mechanism in Collections API (bug 910311)
fileviewer style tweaks (bug 911813)
amp your fx homepage promo (bug 912712)
Merge pull request #1097 from ngokevin/ampfirefox

amp your fx homepage promo (bug 912712)