Support tree-centric searching

Default search filters using a `plot_id IN (...)` clause resulted in a
huge database hit and sometimes confused the planner.

Since we control how searches are mapped we can map the searches
directly onto trees.
Send the whole query to the ecoservice

Before we were going through acrobatics to send the right query and
params over the wire. Since the ecoservice should never be public we can
just send it raw SQL (yea!) and remove a ton of support code that wasn't
needed.

In addition we are able to move region detection into python, which is
nice since it makes the Go codebase smaller
Merge pull request #1110 from azavea/topic/more-eco-updates

Topic/more eco updates