Click events generated need to avoid double posting

[ppslim]

This is something that I have seen most obviously before push #63

On the links generated, some occasionally send multiple events to the background to be added to sab.

As these click events are sandboxed in the front end, but processed in the back end, they should be double checked for double submission.

A mini array of clicks in the last 0.5 seconds to reference again. Hell, even just referencing the last click given it's either a double click event, or simply one click generating two or more click events.

[jsterken]

Which sites?

[ppslim]

I am beginning to think this is a touchpad sensitivity issue at the root cause.

Regardless, would be sensible to ensure de-duplication in the click handlers.