Make app_params more abstract

[Metallion]

Currently there's code like this in Kaiserfiles.

app_params " -e CHROME_HOSTNAME=<%= @config[:shared_names][:chrome] %>"

That @config variable is code that gets eval'd in an instance of Kaiser::Cli and thus you need to know the internals of that class in order to write Kaiserfiles and refactoring it becomes hard without breaking existing Kaiserfiles.

When there is time, it would be a good idea to think of a way to make this more abstract.