Bug 1030972 - Import tasks from Bugzilla

This is a post-merge cleanup of some of the code (pep8 stuff) and also addresses two issues:

1. The label for "Import task" has been changed to "Import tasks"
2. On the task detail page, if a Bug id exists in the task name it becomes linkified

Note that I am not sure of my solution to #2. I'm not sure if I should have put the code into the view, and also not sure of my use of `|safe` in the template, so I'd appreciate feedback on those.