Merge branch 'point-context' into point-context-schema

Conflicts:
	include/pdal/Stage.hpp
	src/Schema.cpp
	src/kernel/Info.cpp
Merge branch 'point-context-schema' of github.com:PDAL/PDAL into point-context-schema

Conflicts:
	include/pdal/Stage.hpp
	src/kernel/Info.cpp
useREST still exists, just not switched back on yet
Classification is Unsigned8, not 16
Get rid of very old TODOs and such.
Merge branch 'point-context-schema' of https://github.com/PDAL/PDAL into point-context-schema
Fix typo.
Advertise Dimension info via JSON.
Merge branch 'point-context-schema' of https://github.com/PDAL/PDAL into point-context-schema
Add the rxp reader

RXP is the streaming file format used by RIEGL Laser Measuremnt Systems
(http://www.riegl.com). Support for reading rxp
files is provided by RiVLib, RIEGL's own library which they release for
use by their customers.

RiVLib only supports reading rxp files, not writing them.