No longer stripping dots from downloaded filenames

Previously, the filename (which comes from our database
that validates the filenames at store-time) was
being passed through defaultfilters.slugify and that
was removing dots from the filenames, which was
undesirable.  Also added a unit test for this.

Change-Id: I4fccf2c3e065be1c1ae3826ab5d4bded359db251
Closes-Bug: #1379455
Merge "No longer stripping dots from downloaded filenames"