A new name for OreCzml

Thread to follow what have been said aout it : https://forum.orekit.org/t/renaming-of-oreczml/5172/9

The renaming or OreCzml would be Oresium, il will need a lot of changes:

• All the instances of 'OreCzml' must be replaced with 'Oresium'
• The modules oreczml-core and oreczml-tutorial must be renamed
• A readme must explain that renaming and what was the previous name of the project
• A lot of communication must be made in order to spread the news of the renaming