[Feature] Load & Edit "draft" Polls

[markusphil]

• Add functionality to load and update polls as long as they aren't active or closed. (This should work analogous to the templates)

• Is it posible to protect active/closed polls from mutation via firebase rules? => it is: https://firebase.google.com/docs/rules/data-validation?authuser=0#use_existing_data_in

• disable the option to change state back to draft once there are answers.

[dkellner]

It should also be possible to delete polls, at least as long there are in the 'Draft' state.