Feature/igw attachment

[caiovfernandes]

Add the attachInternetGateway boolean variable to attach or not a Internet Gateway within a public subnet.

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)
• I have read the CONTRIBUTING.md doc.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

[RaphaelMacedonio]

lgtm