Qualys Vulnerability Management integration (#74)

* Add Qualys vulnerability scans

* Use non-zero exit codes for failures

* Convert to strings for Logstash

* Update logstash config for vulnerability scans

* Update README

* Grab all scans statuses

* Add Qualys vulnerability scans

* Use non-zero exit codes for failures

* Convert to strings for Logstash

* Update logstash config for vulnerability scans

* Update README

* Grab all scans statuses

* Fix error: "Cannot convert non-finite values (NA or inf) to integer"

When trying to download the results of Qualys Vulnerability Management scans, the following error pops up:

[FAIL] - Could not process scan/xxxxxxxxxx.xxxxx - Cannot convert non-finite values (NA or inf) to integer

This error is due to pandas operating with the scan results json file, as the last element from the json doesn't fir with the rest of the response's scheme: that element is "target_distribution_across_scanner_appliances", which contains the scanners used and the IP ranges that each scanner went through.

Taking out the last line solves the issue.

Also adding the qualys_vuln scheme to the frameworks_example.ini

README.md

@@ -19,7 +19,7 @@ Currently Supports
 
 - [X] [Nessus (v6 & **v7**)](https://www.tenable.com/products/nessus/nessus-professional)
 - [X] [Qualys Web Applications](https://www.qualys.com/apps/web-app-scanning/)
-- [ ] [Qualys Vulnerability Management (Need license)](https://www.qualys.com/apps/vulnerability-management/)
+- [X] [Qualys Vulnerability Management (Need license)](https://www.qualys.com/apps/vulnerability-management/)
 - [X] [OpenVAS](http://www.openvas.org/)
 - [X] [Tenable.io](https://www.tenable.com/products/tenable-io)
 - [ ] [Nexpose](https://www.rapid7.com/products/nexpose/)