Point cloud file filter

pcd filter based on boost spirit x3 parser (from boost_matheval)

// -i: input pcd filepath (.xyz/.xyzn)
// -o: output pcd filepath (.xyz/.xyzn)
// -f: filter condition ("x**2 + y**2 < 10 && z > 0.5")

Mesh file filter

// -i: input stl filepath (.ply/.stl/.obj)
// -o: output stl filepath (.ply/.stl/.obj)
// -f: filter condition ("z > 0.1 && x < 0.5")