docs(all): fixes typos and improves readability
docs(cron): adds RST documentation about cron jobs

Converts wiki cron page to RST and references cron in Upgrading docs

Refs #6884
docs(all): improves formatting and comprehensibility of docs

Reworded some paragraphs to make more sense to new users. Applied formatting to some lists and paragraphs
Merge pull request #7087 from hypeJunction/docs

Fixes typos and adds cron RST docs