Add basic Random Page page.

Added a view inheriting from RedirectView to implement Random Page
functionality. Currently chooses from all objects of model Page;
future work may want to restrict this more.

Fixes #346
Remove /tools/ -> dashboard in URLs.

Removed the hardcoded /tools/ -> dashboard app in the main urls.py.  This
means other apps can now define /tools/<whatever> in their urls.py

Using this, I made the random page view appear at /tools/random_page.
Merge pull request #1 from philipn/j-po-add-random-page-page

J po add random page page
Merge pull request #578 from j-po/add-random-page-page

Add basic Random Page page.