Nessus parsing added - needs testing

This commit adds Nessus XML scan output parsing, however it has not been
extensively tested. Two areas that need attention still:

- no t_service_info records are created yet
- more pluginIDs need to be parsed to handle relevant data

Note that the f_vulnid field we're generating is having an impact on
vulns/vulndata_by_vulnid working. Need to fix.
where did ipv4 go?
found it
more motion less filling
Adds NessusAPI

From https://github.com/greencm/python-nessus
Nessus parsing added - needs testing

This commit adds Nessus XML scan output parsing, however it has not been
extensively tested. Two areas that need attention still:

- no t_service_info records are created yet
- more pluginIDs need to be parsed to handle relevant data

Note that the f_vulnid field we're generating is having an impact on
vulns/vulndata_by_vulnid working. Need to fix.
where did ipv4 go?
found it
more motion less filling
Adds NessusAPI

From https://github.com/greencm/python-nessus
workin on it
must be livin in paradise

changed NessusAPI to use os.path.join since Nessus doesn't like // in
URLs.

Haven't tested the download report code yet. Just needed to commit it
for now.
Merge branch 'nessus' of github.com:grutz/Kvasir into nessus

Conflicts:
	controllers/nessus.py
	modules/NessusAPI/common.py
	modules/NessusAPI/utils.py
always look on the bright side of life

lots of little fixes and code shifts. references aren't working entirely
right yet but most everything else seems to work.
code cleanup
fix dynamic field processing
Support severity 0 in charts/stats
ignore None domain entries for adv_stats
Bad merge cleanup
fixing t_vulndata requires