Remove leftover embedded boost cruft

Removes IsEmbeddedBoost() and calls, as well as embedded boost check in
test/unit/CMakeLists.txt.
BPF spatial reference in metadata.
PointContext -> PointContextRef
Merge branch 'master' of https://github.com/PDAL/PDAL into ptctxref
Merge pull request #455 from PDAL/ptctxref

Ptctxref
Merge pull request #453 from gadomski/remove-embedded-boost-cruft

Remove leftover embedded boost cruft
Remove a duplicate include from PointBuffer.hpp

Just a little Monday cleaning.