Create consistent "return variables" for each role

[gregharvey]

It would be really useful if every role had a consistent "return variable" format that users could rely on to contain data they can grab. Original proposal was simply a _result variable, it doesn't matter if it's reset after every role execution, the user can capture it in another variable between role invocations if they want it later.

The original proposal also suggested ensuring any information registered when creating a resource, for example an AWS RDS instance, be captured within _result as an entire element so people don't have to go look that lost data up.

I guess the first job is a proposal for a sensible structure.