Add sections to sidebar

[wayfaringrob]

Allow the user to organize their various selectors into user-defined (and perhaps automatic) categories within the sidebar. Ideally, they would have titles and be collapsible. I am creating a dashboard that will have several filters that each target several layers of block groups, and it would be nice to put these in their own section (such as Block Group Filters) as opposed to other selectors that target auxiliary layers.