Improved boolean based options

[Sandeep Singh]

Ability to set false values to boolean option

cvemap -poc # list cves with poc set to true (as default set to true if not specified)
cvemap -poc=true # list cves with poc set to true
cvemap -poc=false # list cves with poc set to false

This support can be applied to all boolean-based options like:

• poc
• template
• kev