Combat HP Display

A system agnostic module with the purpose of altering the way Token Resource Displaybars are displayed for tokens that enter and leave combat.

The main usecase is to shift from not displaying HP-bars during exploration and roleplay to fully displaying them when combat is started. There's a pair of settings for which Displaybar setting to apply when entering and leaving combat respectively.

I also added in a convert utility in the settings for easily changing the Displaybar value on all actors. The idea is users might realise it's nicer not to have permanent HP bars displayed, and want to change all their actors to for example only show them on hover right away.

A secondary usecase has been added. GridSettings can be set up in the module settings. The purpose is to set the grid as visible when combat starts, making it easy to otherwise have it set as invisible during roleplay or other situations.