Split "map ingestion" interface into its own separate page

[davenquinn]

The map ingestion interface is interleaved with the list of maps in Macrostrat in a way that is not very useful. We need to separate this into a new subpage, and revert the map list back to its original (simple HTML) form.

The "maps list" page created as part of #106 is heavy and has major UX problems:

• Does not work in dark mode
• You lost the numbers, which are important for us (internally) as a quick reference. There should be some way from that page to get the ID numbers or the slugs. And the lower rows without metadata have no way to see which map you're looking at
• You're using a "log-out" icon for a "log-in" action
• If you do link cards, ideally the whole card should be clickable for quick navigation
• The toolbar should not scroll with the page (although the whole concept of having a toolbar on this page is debatable)
• Especially now that the page takes about 300% of the vertical space of the previous version, the sort by primary key inevitably puts the most interesting maps (for editing) at the bottom

Overall, the login/logout functionality is needed, but I think this is a bit of a lateral move in terms of effective user interface TBH.

Originally posted by @davenquinn in #106 (comment)