Openemr render events (#4728)

Openemr render events (#4728)

* Added provider main and portal home render events

Made it so you can tie into events on the page render for both the main
screen (outer shell container that holds the tabs and everything) for th
e provider and for the portal home page (including menu and content
tabs).

* OpenEMR Portal and Main tabs render events

Added events to OpenEMR main tabs screen for outputting html at the end of the body tag and at the start of the body tag.
Added event to filter appointments in the portal home page.
Added event to render output at the end of the portal sections and before the scripts of the portal.
Refactored the appointments into a separate twig file that module writers can overwrite.