roles/taiga: Deploy Taiga project management app

The *taiga* role installs the three components of Taiga:

* taiga-back
* taiga-events
* taiga-front

*taiga-back* is a Python application. Its dependencies are installed via
`pip` in the *taiga* user's site-packages, and the application itself is
installed by unpacking the archive. *taiga-events* is a Node.js
application. Its dependencies are installed by `npm`, and is itself
installed by unpacking the archive. Finally, *taiga-front* is a
single-page browser application that is installed by unpacking the
archive, and served by Apache.

Taiga requires PostgreSQL and RabbitMQ.

roles/taiga/templates/taiga-front.conf.json.j2

@@ -0,0 +1,10 @@
+{
+    "api": "/api/v1/",
+    "publicRegisterEnabled": false,
+    "feedbackEnabled": false,
+    "privacyPolicyUrl": null,
+    "termsOfServiceUrl": null,
+    "GDPRUrl": null,
+    "maxUploadFileSize": null,
+    "contribPlugins": []
+}