fix the crop filter tests
help find plugins in build location
add_test needs WORKING_DIRECTORY set on linux
CropFilter should be built with or without GEOS
remove comments, WITH_GEOS has no meaning anymore
Merge pull request #648 from PDAL/clean-up-crop

Clean up crop
make the crop filter a builtin filter once again
_VARIADIC_MAX must be increased on msvc for gtest
Merge pull request #651 from PDAL/gtest-fix-msvc

_VARIADIC_MAX must be increased on msvc for gtest
Merge pull request #650 from PDAL/make-crop-builtin-filter

make the crop filter a builtin filter once again
Only Windows needs to have the object libraries included in apps/tests