Improve the UX of the Sieve filter editor

[cptsanifair]

🚀 Feature

Actually the Sieve Filter is hard to handle.

Max be its possible to implement things from the following project to upgrade sieve filter technics

Design, Layout, Architecture

https://github.com/thsmi/sieve

[marclaporte]

Thank you @cptsanifair for the suggestion.

https://github.com/thsmi/sieve is AGPL so we can't reuse any code, but we certainly get inspiration for features to implement.

Can you give one example of something better done in thsmi/sieve?

[cptsanifair]

The UI with drag and drop, and switch to source without any metadata-header.
it parse existing source and show it in the UI