Cassandre 6.0.0 released

This is a major release and, sorry for that, it breaks some things (Import filename patterns, files format, Ta4J no more supported, mandatory java 17...).

The main reason behind this is that I needed to fix all the technical debt and complexity that takes me too much time (as Cassandre is just a side project).

I think I managed to make something stable and I hope people will build add-ons on top of it as I want to focus only on the core Cassandre features and not add more and more features with time... For example, I would be happy if someone starts a Ta4JStrategy class as a side project (as I deleted this class!).

This is what's new:

• Runs on Java 17.
• ta4j is NO MORE supported out of the box. I was spending too much time on it, you can still use ta4J of course but you have to integrate it yourself.
• The "id" fields (linked to database) have been renamed to "uid". "id" is not used for general-purpose id (like the id order given by the exchange).
• GraphQL API has been updated to manage the uid fields. Tests have been improved!
• Backtesting data file names and data format has been updated.
• You can now import candles or tickers at startup.
• Deprecated fields have now all been removed.
• Refactored documentation & french documentation added.