Add/edit url only appears if user is logged in
Clarify test for no _project_name

We now provide other data, and still want to be sure that the
test passes.
Insist that all bugs coming in must have last_polled

This is a timestamp that lets us diagnose if a Bug object is stale.
Therefore, it is essential that we get this data from what we import.

This commit adds the validation code to core_importers.py and adds
a test.
Merge remote-tracking branch 'origin/require_last_polled'
Merge pull request #121 from onceuponatimeforever/869

Add/edit url only appears if user is logged in
clarified git instructions 

clarified git instructions by adding "Note that [literal] must be left in the command as shown below"
Merge pull request #122 from CourtneyThurston/patch-2

clarified git training mission instructions regarding literals

Closes: http://openhatch.org/bugs/issue864