Toward #14 - Make a useful troubleshooting page
Created by: MegaphoneJon
This is a partial cleanup - but I'm guessing it'll be easier to review in chunks, so submitting now.
- "General Advice" is successfully rewritten and much condensed.
- I've removed all "Symptoms" and "Solutions" that simply don't apply to modern (>= 4.6) CiviCRM.
- I removed instructions for the Schema Harmonizer tool, which has more up-to-date instructions on its README.
Still TODO:
- There's still a lot of "Symptoms" and "Solutions" which need re-writing, or extraction into a Stack Exchange question (i.e. they deal with some obscure bug).
- Much of the troubleshooting instructions assume Drupal, we should edit out the Drupalisms.