Completed new refcount & property API work. Now make sure it builds for other platforms.
Now builds on Android NDK.
Now setup to build on Windows, which it does.
declared NavigationElementPtr, NavigationTablePtr for consystency
Fixed a bug in SpineItem property parsing.
Fixed some issues with IRI class.
Updated header licenses.
Implemented page-progression-direction on <spine>.
Also includes high-level cover API on Package.
Merge branch 'feature/refcounted' into develop

* feature/refcounted:
  Implemented page-progression-direction on <spine>. Also includes high-level cover API on Package.
  Updated header licenses.
  Fixed some issues with IRI class.
  Fixed a bug in SpineItem property parsing.
  declared NavigationElementPtr, NavigationTablePtr for consystency
  Now setup to build on Windows, which it does.
  Now builds on Android NDK.
  Completed new refcount & property API work. Now make sure it builds for other platforms.