[bug 1032967] Handle unsupported language pairs

Previously we looked at the Gengo service languages list to see if the
src language was supported and went with that. However, that wasn't
correct and created problems. We really need to see if the (src, dst)
pair is supported.

This fixes that.
Merge pull request #318 from willkg/1032967-language-service-not-supported

[bug 1032967] Handle unsupported language pairs
[bug 1026503] First pass at vagrantification

* adds vagrant stuff and provision scripts
* first pass at overhauling docs to use Vagrant rather than explicitly
  walk through how to set up a Fjord development environment
Continued working on docs; ditched hacking howto
Assume VB mismatch and codify the fix in the docs

Ian pointed out that most people will have a mismatch, so we should be
pro-active about that and address it in the docs before provisioning.
This adds the necessary bits to the docs plus it removes the note from
the provisioning script.
Merge pull request #314 from willkg/1026503-vagrantify

[bug 1026503] First pass at vagrantification
[bug 1018727] Backfill translations

This adds a "backfill translations" form to the admin allowing us to
backfill missing translations for responses. It's rough, but probably
good enough for now.
Fix date_end issue
Merge pull request #320 from willkg/1018727-backfillmenow

[bug 1018727] Backfill translations
[bug 1033852] Better handle unsupported src languages

Adds some code to not try known unsupported languages with the Gengo
machine translator. The human translator has a way to find out what
language pairs are supported--the machine translator does not. Thus we
hard-code the list of known unsupported languages so we don't keep
trying and kicking up errors.
Add list of unsupported languages to admin
[bug 1014874] Fix translate ux

This uses the Django messages framework to return a success message to
the user after clicking a translate button which at least tells you that
you successfully pressed the button.
[bug 1038774] Hide responses from hidden products

* hide responses from hidden products on the dashboard
* hide responses from hidden products in the response view
Fix a goof in the last commit

"Unknown" isn't a product and thus isn't in the visible_products list
unless we explicitly add it.
[bug 947767] Nix authentication for API stuff

We don't do any authentication-requiring things with our API, so it's
best to nix the authenticators for now. The authenticators were causing
logged in users to get an HTTP 403 when submitting a Firefox OS feedback
form because of csrf token related things.
Fix response view re: non-existent products

The product field in the feedback_response table is not a ForeignKey to
the feedback_product table. The checking code didn't account for that
and died when the product didn't exist. This fixes that.
[Bug 1030905] fjord feedback api tests for dates

Test the get api when filtering by date.
Add the following tests:
* test_date_start
* test_date_end
* test_date_delta_with_date_end
* test_date_delta_with_date_start
* test_date_delta_with_date_end_and_date_start
* test_date_delta_with_no_constraints
And the following helper method:
* create_test_data
* _test
[bug 935731] Add FactoryBoy

This adds FactoryBoy v2.4.1 to vendor/. We're going to switch to this
because it's the bees knees.
Merge pull request #319 from iankronquist/1030905-more-api-tests

1030905 more api tests
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