Started on array serializations. Beginning with JSON.
json serialization split, plus testsuites.
Moved common json test support code into its own file.
Extended base class with export method, i.e. serialization capability. Format support is dynamic via "package require".
mtime arrays: API tweaks. Implementations re-ordered and tweaked. New json serialization. Testsuite updates.
Cleaned up the multi array doc and implementation. No functional changes.
json serialization for multi arrays. Test suite updates.
Bring basic serialization back to main.