Hack up release-version.sh to allow third-party deploys (1/3)

Make the batch mode flag optional since I need to lock down some
dependency versions.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Hack up release-version.sh to allow third-party deploys (2/3)

Optionally skip pushing since I don't want to actually touch the remote
master at all.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Hack up release-version.sh to allow third-party deploys (3/3)

Optionally add an altDeploymentRepository for the third-party ImageJ
repo, since I want to deploy there instead of wherever the POM says by
default (and in the case of NAR, there is actually *no*
distributionManagement).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>