Add the "start" and "reversed" attributes for ordered lists to the supported HTML subset

Currently only lists starting at 1 are supported, and they must be in ascending order.

It would be quite nice to add the start and reversed properties so that lists in text edits etc. become more flexible.

This could also be controlled through the QTextList class with functions such as:

void QTextList::setStart(int start);
void QTextList::setReversed(bool reversed);
int QTextList::start() const;
bool QTextList::reversed() const;

start can be any number, negative or positive, with a default value of 1.

reversed is true if the list is descending and false if the list is ascending. It has a default value of false.