remove no longer valid pcequal/pcpipeline (now in 'pdal' utility) #436
Merge pull request #436 from PDAL/issues/436-pcequal-pcpipeline-gone

pcequal and pcpipeline obsolete?
back down the boost version requirement to 1.54
remove pcview from apps
Merge pull request #437 from chambbj/remove-pcview

remove pcview from apps
add PCL to the PDAL dependencies documentation, create documentation for
the PCD drivers
Merge pull request #438 from chambbj/pcl-docs

PCL-related documentation updates