Sort plugin events by enabled

### What does it do ?
Sort plugin events on plugin edit page by enabled first. 

### Why is it needed ?
To know what events are associated to plugin without sorting manually.

### Steps to reproduce
1. Open any Plugin from element tree.
2. Go to Systems Events tab
3. Now events are sorted without connect to plugin. So you need to click 2 times (!!!) on "Enabled" column header to see associated to this particular plugin events.