Add a reset styles features in WYSIWYG

See https://forum.xwiki.org/t/line-break-between-paragraphs/18350/

Ideally, for consistency, the user would simply insert a paragraph (Enter key) and then use right click + “Edit Paragraph Properties”, like we have for lists (where we can change the list style). In this dialog, that doesn’t exist ATM, the user would have an option to clear the float around the paragraph (not sure how to present this in a non-technical way).