Update and rearrange TODO
Update and rearrange TODO

Many of the features previously considered essential have over time have
proven to be either ill conceived or just non-essential.

As a result of these learnings the TODO list is restructured to reflect:

* Features and tasks in that are prioritized or in progress (backlog)
* Candidate features that require some thought (icebox)
* Features considered but rejected (trash)

bestie/terrestrial,bestie/sequel_mapper