Help to figure out why sensor.watchman_last_updated changes so often

[dummylabs]

Since watchman catches up every state change of every entity from configuration files, we can fire up a custom event with entity name, which was changed, and its context. The event can also be reflected in the HA event log. This feature should be optional due to enormous amount of possible events.

Inspired by #29 and #50.

[dummylabs]

Another, and simpler, idea could be to add a reason attribute to the sensor, which can be set to (for example):

• Home Assistant restart
• configuration reload
• entity {id} referenced by a config file has changed its state
• etc.