change parsing of encoding on unu save to allow different strategies
and compression levels for gzip and bzip2

----- teem 1.5beta1 cut-off -----

----- teem 1.5 cut-off -----

make unu check on environment variables, so that nrrdDef* and nrrdState*
variables can be set that way

figure out why I was getting a MIO (memory in use) error with 
unu resample when I had the bug in nrrdAlloc_nva (where the
axes sizes were never actually set, so they were both zero).

make darn sure that nobody uses printf(), only fprintf()

standardize and document use of special single characters
for meaning as unrrdu arguments:
M : max position along an axis, equal to #samples-1
# : ?
- : standard in and standard out
any others?