Tabs please

Hi Laura,

I've introduced a new UBB tag, PRE, which keeps the spaces in tact when displayed in the browser.

Unfortunately due to the nature of converting new lines to line breaks in the forum, it does mean PRE text is double-spaced. Will work on this a bit later.

Testing:

This is one sentence

     Indent 1

     Indent 2

            Indent a

            Indent b

     Indent 3



Start of tabs

This

	Is

		Tabbed

End of tabs