Change GAV to intellectualsites domain

[NotMyFault]

For v7, I'd like to propose a GAV change from com.plotsquared:PlotSquared-<module> to com.intellectualsites.plotsquared:plotsquared-<module>.

TODO:

• [ ] Request the creation of a new staging and production database from the OSSRH.
  • [ ] Request to turn of sync of com.plotsquared for this repository
• [x] Update PlotSquared to use and publish the new GAV
  • ~~[ ] Update package names? No objections from my side, but feels a bit unneeded to me too, opinions are welcome.~~
• [ ] Update documentation and highlight change in the v7 release notes.

[Citymonstret]

I'm fine with this, as long as the package names remain the same. We've already switched out package names once, and it's a very unnecessary (completely) breaking change.