Re-write content on general troubleshooting advice

Created by: seancolsen

After imported content into this guide from the wiki, I re-organized a lot of content on troubleshooting into one page. On this page, I created a section at the top for "General advice", and into that section I placed all the general troubleshooting advice I found scattered across many wiki pages. I think this is a good start, but now the section really needs to be updated to point people to Stack Exchange and Mattermost instead of the forums.

But wait! We already have all these pages which say similar things...

• https://docs.civicrm.org/user/en/latest/the-civicrm-community/the-civicrm-community/
• https://docs.civicrm.org/dev/en/latest/basics/community/
• https://civicrm.org/get-involved
• https://civicrm.org/community
• https://civicrm.org/help

Do we really want to create another one?? Maybe. I don't know.