DMRECON: discard dz and conf maps by default

We don't need those often, so don't clutter the views.
DMRECON: add options --keep-dz and --keep-conf

libdmrecon doesn't write those by default, so add an option.
UMVE: add options to keep dz and conf maps

libdmrecon doesn't write those by default, so add an option.
Merge pull request #33 from Waldteufel/discard-maps

UMVE: added options to keep dz and confidence maps