Specify jigsaw module name

[Former user]

Using Nimbus-SRP from jigsaw projects is difficult because when getting it from Gradle, the filename is srp6a-2.1.0.jar, where "srp6a-2.1.0" is not a valid jigsaw module name.

Please modularize Nimbus-SRP or at least specify an Automatic-Module-Name in the manifest.

[simon]

Please supply a PR for the manifest. Thanks!