[entropy.db] delete inverse actions from treeupdates actions

For instance, if we have moved a to b and then we decided to move
b back to a, Entropy will keep flip flopping from one to another.
This commit makes possible to filter such actions so that only
the last one is considered in the end.
[entropy.client.interfaces.db] reduce delta threshold for EAPI3 to 100
[entropy.db.sql] retrieveTreeUpdatesActions, listAllTreeUpdatesActions: order results by date
[entropy.server] _rewrite_treeupdates: filter out duplicated actions
[entropy.server.interfaces.db] _rewrite_treeupdates: use list instead of set

We want to preserve the order and all_actions_cache is already filtering
out the duplicates.
[RigoDaemon] randomize _auto_repositories_update to avoid bursts of requests
Release Entropy 202
Tagging Entropy version 202
[Rigo] cope with invalid icon data path
[Rigo] rate limit requests towards the web service
Release Entropy 203
Tagging Entropy version 203
Merge remote-tracking branch 'upstream/master'