PerformanceScalePlugin: Add plugin for automatically adjusting error target based on performance, cache

[gkjohnson]

If the cache becomes full then automatically lower / raise the error target until it's not. Can also consider performance when calling "update". The recent "update on change" plugin may make it difficult to measure update performance.

[gkjohnson]

The recent "update on change" plugin may make it difficult to measure update performance.

Only considering updates > 0.1 ms or so for impacting cache etc adjustments may be good enough. Though fade tiles plugin on it's own may push that above 0.1ms? Perhaps a event flag indicating whether a full update iteration has been made or not is best.