Added deboard command

[ompatil-15]

Added deboard command for organisation data deletion

Closes issue #62

Example Usage:

• mantis deboard -o example_org
  • Deletes all data related to an organisation.
• mantis deboard -o example_org -s example_domain
  • Deletes all data of a specific subdomain of an organisation.
• mantis deboard -o example_org -a
  • Deletes all data of an organisation from the assets collection.
• mantis deboard -o example_org -a -f
  • Deletes all data of an organisation from the assets and findings collections (supports any combination).
• mantis deboard -o example_org -a -s example_domain
  • Deletes all data of a specific subdomain of an organisation from the assets collection.

[0xbharath]

Thanks for the PR. We are reviewing it now.