adding extra colormaps

Extra colormaps for Veusz, stored in LUTs.npz. There are probably far
too many for ordinary users - these can easily be removed or modified
from the numpy zip.
Contents: All matplotlib cmaps, cmaps from PV-WAVE/IDL, cmaps from Cameca.
All colormaps are stored as matplotlib LUTs in LUTS.npz. These are
converted to the RGBA tuple format used in Veusz's colormap.py.