Initial commit.
Add support for most API calls; lots of reorg.

- JsonExtractor -> JsonReader
- Don't have "...AndClose" methods for InputStreams.  Turns out it
  doesn't really help that much.
- Rework DbxDataObject to do single-line and multi-line dumps.
ChangeLog: Prep for 1.7 release.
examples/pom.xml: Add placeholder for release staging repo.
ReadMe: Update version number.