Implement intrinsics for ccdeploy

[Eric Z. Beard]

Done:

• Ref
• Fn::GetAtt
• Fn::Sub

TODO:

• Fn::Base64
• Fn::Cidr
• Condition functions
• Fn::FindInMap
• Fn::ForEach
• Fn::GetAZs
• Fn::ImportValue
• Fn::Join
• Fn::Length
• Fn::Select
• Fn::Split
• Fn::ToJsonString
• Fn::Transform

[Eric Z. Beard]

Implemented partial support for intrinsics in #239