Add IcingaNodeName script variable, set as check source (WIP).

Fixes #5471
Fixes #5473
DB IDO: Add check_source to statehistory table.

Refs #5470
DB IDO: Add icinga_node to *history tables.

Refs #5470
Merge branch 'feature/ido-hist-node-5470' into next

Fixes #5470
Add check source to external commands / check result reader.

Fixes #5615
icinga check: add *_execution_time, num_{services,hosts}_* state/pending/flap/downtime/ack as perfdata.

Fixes #5440
Fix including a non-existing directory exception requires path information.

Fixes #5618
Add Cluster Health Check.

Fixes #5438
Fix validation for the "authorities" attribute.

Fixes #5593
Fix: PostgreSQL's GetAffectedRows() function always returned 0.

Fixes #5628
Livestatus: Set host checks / freshness to 1 for compatibility reasons.

Fixes #5629
Move Check Stats into CIB.

Fixes #5617
Implement recursive includes for the cluster component.

Fixes #5304
Move ClusterCheckTask into the cluster component.

Refs #5438
Make Visual Studio 2010 happy (maybe).

Fixes #5637
Make script variables constant.

Fixes #5446
DB IDO: Fix deleted config objects not marked is_active=0.

Fixes #5643
Add {active,passive}_checks_{1,5,15}min to icinga check perfdata.

Fixes #5649
Cluster: Periodically dump status json.

Refs #5444
Refactor ClusterCheckTask based on cluster status.

Refs #5444