Improvements on translation-subscriptions spec

Translators in the future will be allowed to subscribe to changes in a given
POT file as well as in the actual PO, with translation changes and additions coming from different translators.

https://launchpad.net/products/rosetta/+spec/translation-subscriptions

Following the above spec, imagine that I'm subscribed to 50 different templates, some of which might be big. Now imagine that everyday different translators contribute a little bit to the translations of different templates, changing translations, adding translations. Sending a daily email for each of the 50 templates might become a problem for you and for the subscriber, specially in very active teams. Therefore I suggest that only *one* maximum email is sent per each day or two (if there were changes in the subscribed templates, of course), with a report like this, for each of the templates:

[Where (hoary, breezy,...product,etc.), with link][Template Name]
* [Last Statistics: Translated, Untranslated, Fuzzy]
* [New Statistics: Translated, Untranslated, Fuzzy]
* [Translators involved in the change, and their team]
ALTERNATIVE 1 (better for the sake of simplicity in the email the subscriber receives, since it is more summarized and only goes check changes in the templates he wants):
 * [Check this history change at: provide launchpad link]

ALTERNATIVE 2 (include the full report in the email)
* [POT File Changes]
   [First line of the msgid]
   [First line of the msgid]

* [PO File Changes]
   [Translator X][Team][First line of the msgid][Mark]
....
   [Translator Y][Team][First line of the msgid][Mark]
....

--//--
Mark can indicate if it is a new translation or not.