JPSSnagg

New feature: -A aggregation time feature added. (JPSS-54)

Initial implementation of test and code to support the -A aggregation time option.

test/testfiles/usage.txt:
test/testfiles/usage-bad-option.txt:
    updated with the addition of -A option.
test/testfiles/redro4.txt:
test/testfiles/redro32.txt:
    added for new tests of the -A option.
test/testnagg.sh:
    Added tests to validate the -A option.
src/nagg_main.c:
src/nagg.h:
src/nagg_posix.h:
src/nagg_options.c:
src/nagg_select_granules.c:
    Added new code to support the -A option.
doc/RELEASE.txt:
    Updated with the addition of -A option.

Tested: koala (linux 64), jam (linux32).