caltechlibrary/dibs: Release 0.4.0

This version implements an interface for starting the IIIF image processing workflow. This is implemented in the `dibs/templates/list.tpl` template file, with an an addition to `settings.ini`. It interacts with the "available" column in the `/list` page. Other changes and issues fixed: * Fix issue #81: anonymize user names in trace/debug logs. * Fix issue #75: allow force-viewing item pages; this uses a query parameter to the item page URL. * Fix issue #71: add interface to trigger IIIF processing workflow. * The size of the LRU cache for IIIF images is configurable using variable in `settings.ini`. * Tweak some user interface elements. * Take out "Caltech" from email template, to make it more generic. * Refactor some internal code to further simplify the logic. * Fix more miscellaneous bugs. * Do some housekeeping on files.