YAML config and refactoring

Kvasir configuration is now primarily driven through a YAML file. This
means the days of editing python files for settings is nearing an end!
A sample YAML file is included and Kvasir will not start if the YAML
file is not found or invalid.

This new configuration required moving around the global settings to its
own models file. db.py must first process the YAML configuration to
generate the global settings variable.

Settings for Metaasploit and Nessus have been removed from the auth_user
table. Functions have been declared to handle these.

A hosts.py skaldship module has been generated to provide all host-based
functions.

Other tweaks and twerks.
Adding pwnwiki and exploit-database settings
Updates for yaml
Merge branch 'yaml_config' of https://github.com/grutz/Kvasir into grutz-yaml_config

Conflicts:
	controllers/nmap.py
	models/db.py.sample
	modules/skaldship/general.py
fixup