Update IAM Policy Statements to support multiple resources

[bpholt]

This should make writing policy statements that affect multiple resources a lot cleaner. Right now, AFAICT you have to break them out into multiple statements, which is hard to read in the generated template and, eventually, the generated policy. Multiple resources are supported by IAM.

This should be backwards-compatible with the exception that one has to

import com.monsanto.arch.cloudformation.model.resource.PolicyStatement._

to get the implicits. I'm open to moving them to another location that is more likely to already be imported if someone has an idea of where that might be.

The generated JSON will now always contain an array for the Resource field, but that should have no impact as far as CloudFormation/IAM are concerned, and matches the behavior of the Python AWACS library.

[bkrodgers]

What if we put them in the Token companion object with the other implicits, i.e., somewhere around here:
https://github.com/MonsantoCo/cloudformation-template-generator/blob/master/src/main/scala/com/monsanto/arch/cloudformation/model/AmazonFunctionCall.scala#L227

For one thing, I think they're generic anyway and may come in handy in other cases. And for another, people are probably already importing either Token._ directly, or are getting it because that import is in model's package object. At least in my templates,

Can you think of any issues having this conversion available globally like that?

[bpholt]

@bkrodgers Putting them in the Token companion object works for me. I was able to remove the explicit imports I had to add before, so I think it’s likely to provide the backward compatibility we’re looking for. Updated in 488e567.

[bkrodgers]

Thanks, LGTM!