This is the second half of D341.
This allows at least relics to have no health (#5007). And adds a player colour background to panel entities (#5014).
Also the capture bar will be shown for panel entities and a capturable-tooltip.
In a later diff, the removal of the health requirement can be extended (e.g. garrisonHolder is required to have health, return resource in UnitAI requires the entity to have health).