Don't overwrite status to email opened if the user has already clicked the link or submitted data. Fixes #529

Closes #215 
Closes #128 

Routes:
/api/groups/summary
/api/groups/:id/summary

The UI is now using these routes for the "Users & Groups" page.

Leveraging the new campaign summary API endpoints in the web UI to help with displaying large campaigns.

/api/campaigns/summary
/api/campaigns/:id/summary

This is part of #505

Better gzip compression to save bandwidth.

Fixes issue with cropped attachments.

Thanks @ss23!

Thanks, @svigne1!

Fixes #53 

Moved drawing the users datatable out of the addTarget method for faster rendering of a large number of imported records.

This pull request fixed XSS vulnerabilities identified in the gophish admin panel.

**Important: These vulnerabilities could only be exploited if someone had access to the admin panel already, and could only exploit the vulnerability against the same account.**