ZRAM status

I’ve rewritten part of post #1, giving instructions what to do on OH upgrades so we don’t waste precious memory for the cache.
I’m hesitant for now to automate that (too risky to fail) but I would like to point ZRAM users at it.
@Benjy: My idea is to print a link to this thread when a user runs openhab-cli clean-cache, wdyt?