Clarify that PHPIDS is not just about inputs which are saved to the
database, but actually all inputs (e.g. GET params) even ones that
aren't saved to the DB.

Fix Wiki URLS to point to correct docs url

Import "Verify a bug fix" wiki page

https://wiki.civicrm.org/confluence/display/CRMDOC/Verify+a+bug+fix

Clean up mkdocs.yml

Migrate CiviMail Reference Document

(They don't show up as sub-lists unless you use 4)

Migrate payment processor docs from wiki

https://wiki.civicrm.org/confluence/display/CRMDOC/Example+of+creating+a+payment+processor+extension

https://wiki.civicrm.org/confluence/display/CRMDOC/Testing+Processor+Plugins

https://wiki.civicrm.org/confluence/display/CRMDOC/Create+a+Payment-Processor+Extension

https://wiki.civicrm.org/confluence/display/CRMDOC/What+is+a+Payment+Processor

Fix typo in Mkdocs.yml

Import wiki content about Smarty templating