Remove unused assignment
Use Bacon.never instead of conditional plugging
Simplify return value and make helper function

Had to commit these together because they were both affected by a similar change.
Move things around
Refactor ui tests to make writing tests faster
Add UI test for plot detail

This test was created in conjunction with fixing an actual bug that was discovered in an earlier iteration of this branch and almost introduced.
Merge pull request #941 from steventlamb/topic/cleanup_doc_refactor

Topic/cleanup doc refactor
Fix broken references
Add ui test for plot detail edit add tree cancel

will verify issue #943.
Create ITreeRegion table in treemap app
Move all ecobenefits code to treemap app (fixes #805)

* species.py: move to treemap
* init.py, views.py and util.py: merge into a new ecobenefits.py
* urls.py, models.py: merge into their counterparts in treemap
* tests.py: move to tests/ecobenefits.py
* update import statements

Also: remove unused URL and view ("eco/benefit/tree/" and tree_benefits_view)
Merge pull request #944 from RickMohr/kill-ecobenefits-app

Kill ecobenefits app
Add ITreeCodeOverride table

ITreeCodeOverride table
* Stores "species + region --> itree code" overrides
* Declares that a species/region pair must be unique

Update itree_code fetcher (itree_code_for_species_in_region) to use this logic:
* Look first for an i-tree code override in ITreeCodeOverride table (using in-memory version if supplied)
* If no override, find i-tree code in CODES dict as before

Also:
* Delete unused function get_codes_for_species()
* Conversion function _trees_for_eco() now used only locally
* Rename species_in_region() helper as has_itree_code(), and simplify
* Simplify language in plot_eco.html (fixes #925)