Matías Bellone

This is a huge refactoring of the tests and moving some non-plugin specific code to a separate library. I also tried to make the plugin code actually use some better...

Based on #47 I have refactored the download code so that you can now specify per-artifact step and/or build. The `step`/`build` configurations on the plugin level will be used as...

Same intention as #108, but implemented differently. This way, we do not have to update all the tests due to the new option Closes #107

According to [AWS ECS RunTask documentation](https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_RunTask.html#ECS-RunTask-request-capacityProviderStrategy), to run a task in a cluster's default capacity provider you need to leave both CapacityProviderStrategy and LaunchType blank: > If no capacityProviderStrategy or...