Prevent editing of camps related to past events

[NitayRabi]

Overview of the problem

Currently past events (such as Midburn2018) are editable - this shouldn't be functional after the event.

Steps to Reproduce

1. Navigate to camp management (in past event)
2. Editing is available.

Expected behavior

Editing old camps related to old event shouldn't be possible.

Actual behavior

Editing camps related to old event is possible.

[NitayRabi]

Will be fixed via #991