Add active status to "add tree" navbar item.

Fixes #735.
Display custom logo on edits page. Fixes #876.
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
Fix lint
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)
Merge pull request #919 from ahinz/fix/735/add-active-state-to-add-tree

Add active status to "add tree" navbar item.
Merge pull request #920 from ahinz/fix/876/custom-logo-on-edits-page

Display custom logo on edits page. Fixes #876.
Merge pull request #946 from RickMohr/itreecode-table

Add ITreeCodeOverride table
Use django.test.TestCase rather than explicit tearDown
Fix lint
Add bulkCreate helper to otmTypeahead
Fix delete_tree url to match routed args
Pass treeId through from plot_detail endpoint

Tree ID is always passed through (either as a number or null) to ajax callers of the plot_detail endpoint. plot.js listens for treeId values and puts them into the edit form.

This is required so that we can put the newly created tree id into the edit form. Having the id in the edit form, in turn, is required in order to be able to delete a tree after adding it, without reloading the page.
Add frontend support for tree & plot deletion
Show deleted trees in recent edits table
Merge pull request #951 from steventlamb/topic/delete_tree_frontend

Topic/delete tree frontend