Fix a typo in melange back pressure code.
Remove all uses of get_array() outside of FEM code.

Also: fix a bug in POConstant::shelf_base_temperature().
Clobber a compiler warning.
Delete all debian [meta]package stuff. Remove manpages.

It never worked reliably enough to bother. (This is mostly my fault,
though.)
Rename examples/piktests -> examples/marine.

Also: improve examples/marine/circular/circular_dirichlet.py.
Add examples/marine/melange.