Restrict action spamming

[aatkin]

Currently users can unrestrictedly click actions, which perform potentially long-running requests. REMS tries to process these requests concurrently, which (at this time) may lead to process hang. Spam-clicking an action is likely a symptom of unresponsive UI.

Add "double-click listener" which prevents action from being re-submitted before request has returned:

• rems.application/actions-form
• rems.administration.blacklist (add/remove)

Other implementation concerns:

• Indicate action processing to user Loading indicator for action button #3210