make certain edge case of viewing mm map much faster

(if you load an app with a bunch of missing mm references don't save it
once for every missing reference)
use iter_docs to get multimedia items out of couch

resulted in a 20 second to 8 second load time for a local build with
about 400 media references
clean up how psi hacks are done
newline
whitespace
Merge pull request #395 from dimagi/psi

hard code psi village classes to what they want (Case:62047)
update psi
remove unused imports
Merge pull request #396 from dimagi/mm-zip-to-files

multimedia zip file changes
Merge pull request #394 from dimagi/mm-speedup

multimedia map optimizations
Merge branch 'master' into case-config
Merge branch 'case-config' into staging2