Jormungandr drop db

Drop usage of database in Jormungandr:
We check in every instance if the id is in it or not, then we cache it.

To cache we use: https://pythonhosted.org/Flask-Cache/

Thus we no longer need aggregate_places \o/.

Some improvements has to be made: 
 * we need to paralellize calls to kraken.
 * Maybe we can cache per request the region.
 * It would be great if id request to kraken were computed before others

no timeout for this cache ? since it is wiped out with the data reloading ?
if so a comment would ease the understanding :)

from a general point of view shouldn't we think about the configuration of the cache (for the production plaftorm for example) ?