duply: upgrade 1.6.0 -> 1.7.3

Changes since 1.6.0:

1.7.3 (3.4.2014)
- bugfix: test routines, gpg2 asked for passphrase although GPG_PW was set

1.7.2 (1.4.2014 "April,April")
- bugfix: debian Bug#743190 "duply no longer allows restoration without
   gpg passphrase in conf file"
   GPG_AGENT_INFO env var is now needed to trigger --use-agent
- bugfix: gpg keyenc test routines didn't work if GPG_PW was not set

1.7.1 (30.3.2014)
- bugfix: purge-* commands renamed to purgeFull, purgeIncr due to
   incompatibility with new minus batch separator

1.7.0 (20.3.2014)
- disabled gpg key id plausibility check, too many valid possibilities
- featreq 7 "Halt if precondition fails":
   added and(+), or(-) batch command(separator) support
- featreq 26 "pre/post script with shebang line":
   if a script is flagged executable it's executed in a subshell
   now as opposed to sourced to bash, which is the default
- bugfix: do not check if dpbx, swift credentials are set anymore
- bugfix: properly escape profile name, archdir if used as arguments
- add DUPL_PRECMD conf setting for use with e.g. trickle