[WIP][v7] Deprecations

[tabacitu]

Let's list all of the deprecations we plan to do in the next version, and why:

• [ ] 🟡 deprecate ->addColumn() because ->column() is a complete replacement;
• [ ] 🟡 deprecate ->addField() because ->field() is a complete replacement;
• [ ] 🟡 ??? deprecate ->addFilter() because ->filter() is a complete replacement; not sure;
• [ ] 🟡 ??? deprecate ->addButton() because ->button() is a complete replacement; not sure;