add management command to assign upload_timestamps

introduced in bug 1366; The next revision should be checked out immediatelly
after this management command has been completed (not earlier or later)
query episode actions based on upload_timestamps (bug 1366)
Merge branch 'couchdb' into upload-timestamps

Conflicts:
	mygpo/users/_design/views/device_history/map.js
	mygpo/users/models.py
Merge branch 'couchdb' into upload-timestamps

Conflicts:
	mygpo/users/_design/views/device_history/map.js
	mygpo/users/_design/views/episode_actions/map.js
	mygpo/users/_design/views/history/map.js
Merge branch 'master' into upload-timestamps
Merge branch 'master' into upload-timestamps
update assign-upload-timestamps management command
keep actions sorted by walltime timestamp
evaluate datetime.now() on each call
set upload timestamp for new episode actions
add comments to timestamp definitions
add upload timestamp to manually entered actions
use integers as upload_timestamp
Merge branch 'master' into upload-timestamps

Conflicts:
	mygpo/users/_design/views/episode_actions/map.js
make test pass again
Merge branch 'master' into upload-timestamps
remove spurious prints
fix typo
return msg in bad request response in Advanced API
add some API test cases