Refactor to use Parameter generically for Environment as well as Sett…

[josmo]

…ings and remove Variable

@bradrydzewski When looking at the map fix in #3 and, I was trying to test out environments and I expected the environment key to act in a similar fashion to the settings key.

right now something like

environment:
  arrayenv:
  - thing1
  - thing2

gets an unmarshall error and I would expect it to work in a similar way to settings

I was going to propose the change in an issue, but it was pretty quick to do. if this issue and #3 are merged then the behavior of environment and settings are essentially the same (settings adding "PLUGIN") and more predictable

[bradrydzewski]

The environment should only accept the following formats:

environment:
  KEY: value

environment:
  KEY:
    from_secret: SECRET

In this case we would not expand the scope of this field to accept complex data structures.