dogeparser: improve handling incomplete documents

Doge doesn't like incomplete DSON document.  ManyParseException needed.

All scanner functions raise ManyParseException now when they encounter EOF before they can consume any characters.

Added new tests for this, and also for empty objects, which fails miserably.
dogeparser: more incomplete document tests
dogeparser: fix parsing empty objects
dogeparser.tests.test_parser: add empty array tests

They pass, such amaze