Disabled timymce for posting and editing posts

The reason is that editing or preview may mess up the formatting of the post.
Removed <p> tags in bbcode lists
Revert "Add empty paragraph to quote when replying with quote to make it possible to start writing a paragraph directly"

This reverts commit c85e366a21b6db01a08c36f5059a4559bc7e6886.
Not needed anymore when tinymce is disabled.
Changes to styles to accommodate the removal of <p> tags from bbcode lists