Allow global parsing of non-positionals

[pvandyken]

To meet the needs for our current implementation, the argument parse stops looking for Shapes, Flags, and Keywords as soon as it runs out of Positional args and meets a new unidentified argument. This commences the TailArg, and everything thereafter falls into that. It would be good, even for kslurm's needs, to allow global parsing of non-positionals, and only collecting unidentified args into a TailArg.

This will require a 2 pass approach: First one pass ignoring all positionals and aggregating keywords. Then separate out all the non-positionals. Then pass the remaining positionals and unidentified back into the parser for Positional parsing and collection into the TailArg.