Time-stamp: <2007-02-10 17:20 olenz>

Done:   
- merged set_unitcell, set_unitcell_vmd into pbcset
- merged get_unitcell, get_unitcell_vmd into pbcget
- renamed set_unitcell_xst to pbcset_xst
- renamed unitcell_vmd2namd to pbc_vmd2namd
- extracted pbc_namd2vmd from set_unitcell
- renamed write_xsc to pbcwrite_xsc

Removed procs, because they don't fit into PBCTools:
- read_xst
- flip_unitcell_angles
- draw_pbc_cell
- draw_pbc_vectors
- draw_pbc_hexagon
- draw_pbc_hexagon_debug
- draw_pbc_boundary
- waterboxsize
- cut_pbc_cell
- draw_minmax_box

To be done:
- test pbcset: with NAMD vectors
- test pbcset_xst
