Redo Path parsing?

[James Powell]

Working on the second part of #82, ran into difficulties. Really want a path like $.myitem[#] to:

• insert in array if myitem exists as an array
• create a 2-element array myitem containing the original myitem and teh inserted element
• create a 1-element “myitem” array if myitem not found

Getting that to work is hard, and would be easier if we parsed out teh full path info at teh start of a search (rather than parse it bit-by-bit at each level). This rework would also (hopefully) improve performance by avoiding redoing parsing (such as in going through a long array of clusters).

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[James Powell]

Note: might help with #63