[api] having an index on cache_lines should make it bit faster

Mainly slows down the event processing
[api] call the event jobs delayed

As we keep a transaction open for 1000 events, we lock quite some tables
to parse issues, clear cache lines, ...
[backend] make sure not to include our own build results in meta calculation
[api] Adjustments in commits feed to be more human and aggregator friendly
[api] add db index to ProjectLogEntry#datetime
[api] ProjectLogRotate marks ALL old events as logged
[api] add errbit_host line to options.yml.example again
[dist use only local socket and no port for mysqld during test suite run
[api] add the possibility to subscribe to events

You can subscribe globally or on project/package leel if you want to
get notifications (not yet implemented obviously) for events either for

 - none (overwriting more global defaults)
 - project maintainership
 - package maintainership
 - all
[api] start of an action mailer for events
[api] add current hermes templates in erb format
[api] move the notification templates in the right place