[DBTablesMonitoring] Add a new column "unified_event_id" to incidents table
[DBTablesMonitoring] Copy values in events.unified_id ot incidents.unified_event_id on updating the DB
[UnifiedDataStore] Store events to DB before execute actions

It's needed to pass valid unifiedId to actions.

TODO: Investigate side effects
[IncidentSenderRedmine] Fill unifiedEventId of IncidentInfo
[IncidentSenderRedmine] Don't build monitoring server's URL when the event is self-monitoring event
[DBTablesMonitoring] Use unifiedEventId to join incidents table to events table
[testIncidentSenderRedmine] Fix broken tests

They are concerned with unifiedEventId which is recently added.
[testDBTablesMonitoring] Fix broken tests

They are concerned with unifiedEventId of IncidentInfo which is
recently added.
[DBTablesMonitoring] Fix a bug that unifiedEventId isn't filled on getting incidents
[testIncidentSenderRedmine] Fix a failed test "test_parseResponse"

Fill unifiedEventId of IncidentInfo with an appropriate value.
[DBTablesMonitoring] Fix a bug that unifiedEventId is cleared unexpectedly on updating an incident

We should't support overwriting it because unifiedEventId of an
incident is never changed.
[DBTablesMonitoring] Make index of unifiedEventId in IncidentInfo

In the previous implementation old self-monitoring events are
overwritten on upserting because serverId and eventId of
them are duplicated.
[DBTablesMonitoring] Make indexes for identifier in incidents
[testDBTablesMonitoring] Fix broken tests

The order of incidents are changed by adding indexes.
[DBTablesMonitoring] Fix order of index definitions of incidents
[testDBTablesMonitoring] Fix broken tests

I forgot to update location of incidents.
Merge pull request #834 from project-hatohol/issue-725-4

[server] Fix a bug that a self-monitoring event is tied to an incorrect incident (issue #725)