Fix Windows linker errors (LNK2005, LNK2019)
add filters.attribute to stage list
Fix setting header system ID.
Merge pull request #566 from PDAL/windows-fixes

Fix Windows linker errors (LNK2005, LNK2019)
Add PDAL_ADD_TEST cmake macro

This macro can be used to add test executables to the project.
Especially useful for plugins.
Update PDAL_ADD_PLUGIN target_link_libraries

Remove PCL_LIBRARIES and add PDAL_LINKAGE.
Add the rxp reader

RXP is the streaming file format used by RIEGL Laser Measurement 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.