Fortiguard url taxonomy

[srilumpa]

This addresses #295 by allowing customization of the malicious and suspicious categories through the Cortex configuration.

Instead of having Malicious Websites hard-coded as the only malicious category and Suspicious Websites hard-coded as the only suspicious category (which, by the way, is not listed anymore as a FortiGuard URL category), the list can be configured in Cortex. This will allow more flexibility to users to define what is malicious and what is suspicious according to their company/internal/personal Security Policy. Every category not listed in those two lists will be considered as safe.

Beware, the comparisons are, for now, case sensitive.

The full list of categories can be found at https://fortiguard.com/webfilter/categories.