Added simple sticky headers to sidebar.
Made headers push out of the way.
Fixed lint.
Moved heading height to a variable.
Autocomplete results now display above sticky headings.
Merge branch 'simple-sidebar-sticky-headers' of https://github.com/huwshimi/juju-gui into sticky-header-redux

Continuing development on this feature branch.
Refactored the sticky header code to work for both the featured charm list and the search result list.
The code has also now been documented and cleaned up a little bit