backend: poll scheduling and results calculations

[x] coding: (re)schedule polls on proposal start/end changes and/or new proposals
[x] coding: kill existing threads/timers when proposal changes
[x] coding: start new threads/timers when proposal changes
[x] coding: tally votes on poll 'ended' (end date timer fires)
[x] coding: generate deliver poll results effects to booth subscribers
[x] validation: confirm poll has status is valid (e.g. 'scheduled') before allowing changes
[ ] validation: confirm end date > start date
[ ] validation: ensure start/end date not in past
[ ] validation: error effects on invalid status (anything other than 'scheduled')
[x] integration: integrate action/reaction/effects flows w/ UI
[ ] testing: test action/reaction/effect flows w/ UI
[ ] testing: poll calculations and results
[ ] security: do not allow any entity except for booth owner to modify proposals

NOTE: Delegation feature not part of this task.

Test polling start/end timers.

Assuming changes to proposal poll start/end time:

1) ensure updates to proposal cancel existing timers 2) start new ones for new start/end timers

Run thru each vote in a specified proposal by summing vote count per choice.

e.g.

{ "Allow": 14, "Reject": 20 }

calc w/ .5 score:

Result: Proposal rejected

holium / ballot