Disturbance Category to not be required

[pascalflohr]

The Disturbance Category field has been made required (during the making of more fields required/mandatory again issue), but should be optional.

So Disturbance Cause and Effect, Effect 1 and Effect 1 certainty, and Date should be required.
Category, and Effects 2-5 and Effects 2-5 certainties should be optional.