Add more HTML tags to the input format

The HTML tags accepted from l.d.o are the same accepted by default on d.o.
Different roles exist in d.o, and to some of them is associated a more extensive input format. I am not sure if the same is valid on l.d.o.

Table HTML tags are problematic, as it is possible to make a page unreadable by using the wrong value for an attribute.

I'd love to hand out more tags in some form, but I need to look at what other sites allow and what are our rules. Eg. what can groupg.drupal.org team members post. As part of the drupal.org redesign, we are also trying to get the input formats closer, so when moving among sites, you'd not have the reset your mind on your input formats.

I've added a "Rich HTML" input format which can be used for this input. I kept the simpler Filtered HTML as default, so that comments, etc. have less chance to break whole pages.

Table tags were added to the base Filtered HTML format on drupal.org (based on #558398: Add table elements to Filtered HTML format), and I intended to make the same changes on l.d.o However, this obsoletes the Rich HTML format, since there is no difference anymore between that and the filtered HTML format. Removing the Rich HTML format, which should result in all posts in that format descend to Filtered HTML which is now capable of doing all that. New set of base tags:

<h1> <h2> <h3> <h4> <h5> <h6> <em> <strong> <code> <del> <blockquote> <q> <cite> <sup> <sub> <p> <br> <ul> <ol> <li> <dl> <dt> <dd> <a> <b> <u> <i> <table> <tr> <td> <thead> <tbody>