Corrected a problem when some tags were found between points and lines.

Also removed the header size checking. Could fail when some points were not
used in streamlines.
Merge pull request #7 from jchoude/fix_vtk_vertices

Corrected a problem when some tags were found between points and lines.
Added an issue to manage unordered properties of VTK files.
Merge branch 'master' into add_voxel_size
Changed three enum values for one composite one.