Expansion of Dropdown Feature

[cwitkowitz]

There are several issues with HARP's current solution for browsing and selecting models (i.e., dropdown menu with paths for featured or custom models):

1. the selections are opaque - many model names are unintuitive and offer little insight into what they actually do
2. there is no mechanism for discovery besides loading each featured model or checking the website documentation
3. the dropdown menu itself is unsustainable - it will become less manageable as we continue to add featured models