Implement terraform interpolations

[eerkunt]

Currently, some of the values cannot be parsed because there are some terraform interpolations there. In some cases, it might be impossible to retrieve the data ( e.g. using remote module outputs ).

At least there must be a method for general use for terraform interpolations. Then we can just iterate and add more support on iterations throughout the terraform lifecycle.

[eerkunt]

A fix to this issue will also fix the problem defined in ;

• SecurityGroup Feature:  #57
• Tagging feature doesn't recognize variables #45

[karthikeayan]

Shouldn't this be done at terraform_validate level?

[eerkunt]

The plan is to remove terraform_validate dependency in near future. It has been added too many things within the terraform-compliance that terraform_validate doesn't support. Might be much easier without having the dependency.

[eerkunt]

All interpolations are supported with 1.0.0 release.