[FEATURE] add the possibility to filter events by scan_id

[bWlrYQ]

I thought it might be an interesting feature as it's a need I encountered in my own usage of the BBOT Server API.

[TheTechromancer]

Thanks; this is a good feature and it's already being added here:

• Filtering Improvements #55

[bWlrYQ]

The feature indeed is in that branch, should've checked it earlier... No need to keep the PR open :).