Draft: [dump] add compression option

Add a compression option similar to what pg_dump has.

Usage: (other params exluded for clarity)

 bin/pg_dump_anon.sh -Z ... # default to level 6
 bin/pg_dump_anon.sh -Z9 ...
 bin/pg_dump_anon.sh -Z=9 ...
 bin/pg_dump_anon.sh -Z 9 ...
 bin/pg_dump_anon.sh --compress ... # default to level 6
 bin/pg_dump_anon.sh --compress=9 ...
 bin/pg_dump_anon.sh --compress 9 ...

Can be used in similar fashion as a pg_dump compressed dump:

gzip -dc dump.gz | psql