support setting resource properties

[sinistral]

Being able to set properties is an escape hatch would make it possible use high-level CDK constructs throughout (rather than forcing code that consumes a resource have to be aware of whether it is dealing with a higher-level CDK construct or a CFN resource).

Currently we have to create Cfn* resources and force consuming code to be aware of the differences in property names between the two types of resource.

[lvh]

I don't understand how the ability to set properties would mean you can write code that doesn't have to care about the difference in property names, but I suppose that'd be more obvious once this is implemented :)