ensure method param names

[drshriveer]

Background

→ I ran into two issues with method parameter names:

1. names between input and outputs will conflict if not already named.
2. we do not ensure that fields are named prior to operations may change the size of a parameter list we operate on, and thus cause even the same parameter list to contain conflicting names.

Changes

• always pre-populate method parameter names.
• method returns variables if undefined are prefixed 'ret', inputs are prefixed 'arg'
• use of map to ensure no conflicts.
• attempt to use name 'ctx' for first argument in a function that implements Context.
• attempt to use name 'err' for last argument in function response that implements Error.

Testing

• added minimal testing; this will be verified against stately in tests I cannot codify here.