Use biginteger for audit table primary key. Fixes #259.

Since this is not supported by django
directly (https://code.djangoproject.com/ticket/14286) we can just alter
the table manually.
Hide/show messages during "Add Tree" session per @dboyer (fixes #741)
Merge pull request #915 from RickMohr/fix/741/messages-add-tree

Hide/show messages during "Add Tree" session per @dboyer (fixes #741)
Merge pull request #911 from ahinz/fix/259/use-bigint-for-audit

Use biginteger for audit table primary key. Fixes #259.
Limit photo selection to images. Fixes #296.

This generally makes the file picker only accept image types. The
backend does additional checks since this cannot be relied upon.
Add active status to "add tree" navbar item.

Fixes #735.
Add backend support for static pages

This is designed to allow map deployers to manually add static
pages. This commit is intended to facilitate adding a front end UI later
Allow "writable" if *any* field is writable

Fixes Internal Issue 598
Merge pull request #922 from ahinz/fix/disabling-add-buttons

Allow "writable" if *any* field is writable
Only try to render scalar udfs on plot detail
Merge pull request #931 from steventlamb/bug/fix_plot_detail_rendering

Only try to render scalar udfs on plot detail
Misc diameter calculator updates (fixes #767, #900, #573)

Respect configured "significant digits" in displayed diameter/circumference values:
* Store actual diameter or circumference value in "data-value" attribute on input element
* Prepare display values using "data-digits" from diameter input element
* All values now computed client-side, simplifying server code (rename reset() to init() and call it from constructor)

Also:
* We now round rather than truncating when displaying all floating-point field values
* Allow entering multiple trunks in "Add Tree" mode
* Show units in diameter and circumference input boxes
* Change "Total trunk diameter" field label to "Trunk diameter"
* Change "Total diameter" message label to "Combined diameter"
* "Combined diameter" message now uses no vertical space when hidden
Fixed broken trans tag and changed text, Fixes #926
Fix Indentation
Merge pull request #927 from RickMohr/diameter-calculator-updates

Misc diameter calculator updates (fixes #767, fixes #900, fixes #573)
Merge pull request #932 from maurizi/fixTypo

Fix typo on 404 page
Merge pull request #921 from ahinz/topic/add-backend-static-page-support

Add backend support for static pages
Fix broken test

* "diameter" tag no longer exists
* Add safety code so PyCharm can run our tests
Merge branch 'master' of https://github.com/azavea/OTM2
Add fabric support for code coverage

When running either UI or regular tests specify:

```
coverage=True
```

And a text coverage report will be printed to stdout and a tar called
"coverage.tar.gz" will be downloaded that contains html report.