Rebranded with Leptonite - logos and text

[dennisfurrer]

This is related to: https://app.asana.com/0/1199560399769920/1200490728561060

This changes:

• The package.json and package-lock.json have been modified to be named/described as Leptonite.
• The README has been updated to reflect the rebranding
• Various minor in-code renamings