don't open files to find width for thumbnails

We were opening image files to find out the maximum width that their thumbnails could be.   Now we just assume the largest thumbnail is 1000 so we don't need to open the files.
Unit test for prev commit

required me to add a few things to resources-test/ to set some variables.
Merge branch 'master' of github.com:nla/banjo into hr-thumbnails
Ignore tests

THey work manually but freak out the CI things.
Merge pull request #321 from nla/hr-thumbnails

Don't open files to find max width for thumbnail