adds args,osArgs predefined data for config tmpl

[davidovich]

user can now use {{ index .args 0 }} to get at the passed arguments

invokable arguments can be defined in multiple arrays which will
be flattened. This allows yaml anchor usages:

base: &base
 - a
 - b
...
exec:
  bash -c:
    echo: [*base, c, d]

Without flattening, this would result in:

[[a,b], c, d], but now, it renders nicely to [a, b, c, d]