tighten noauth behavior to be safe, while accepting demo_user submissions

expand tests
make celery tasks run synchronously in tests
display NewSubscriptionErrors as form errors
require subscription end date to come after start date
Merge pull request #2502 from dimagi/double-subscription-submit

Double subscription submit
support device logs in exports again
Merge pull request #2501 from dimagi/eager-celery-in-tests

make celery tasks run synchronously in tests
fix clean_end_date
activate a subscription if it is created on its start date
Merge pull request #2504 from dimagi/active_subscriptions

Active subscriptions
Merge pull request #2503 from dimagi/device-report-exports

support device logs in exports again
speed up loading of project spaces in subscription form
user iter_docs for user.get_forms
simplify
Merge pull request #2506 from dimagi/select2_perf

speed up loading of project spaces in subscription form
remove print statements
check downgrade status and alert for custom role use
Merge pull request #2508 from dimagi/custom-roles-alert

Custom roles alert
update num of users in bubble from 250 to 100
adds field 'Do Not Invoice' to a subscription