refactor the switcher/dropdown

[pacharanero]

=============== Refactor switcher / dropdown ==========

Change the variable from which the current list title comes (Not Patient list - sometimes it's a group)
Move the generation of contents logic out of the view specifically
Get rid of list_slug (Do exclude logic in a function on the server, don't do it in the template, that's PHP.)

WIP towards #1457 and openhealthcare/elcid#1509