Remove unused files

It would appear that the main project was moved into core sub-directory, and
these files didn't get cleaned up.
Correct issue with publishing

Main project doesn't have anything to deploy, and doesn't have config. This
causes a warning when building the project.

Provide the config that is common across all projects in this config file,
but no config for the main project is required.
Fix scm url's

All were pointing at project.name, when in fact they all exist in the same
serenity-core repository
first attempt at replacing custom versioning with gradle-git