Change behavior of Fossil's tag handling.

  1.  All subcommands of command <tt>tag</tt> prepends a prefix <tt>sym-</tt> infront of every
      tag name passed to them. Tags beginning with <tt>sym-</tt> are special in
      Fossil as they might serve as replacement of a UUID they are attached to.<br><br>
      Further, <tt>tag list</tt> will only list all tags beginning with <tt>sym-</tt> but
      with that prefix removed during display as default.<br><br>
      All subcommands can get passed an option <tt>--raw</tt>, that prevent the
      prepending of the prefix <tt>sym-</tt> in front of the tag name. <tt>tag list</tt>
      will report all tags without removing any prefix if called with
      option <tt>--raw</tt>.

  2.  If a command takes a tag name that may be confused with a UUID,
      the command did interpret that parameter as a UUID instead as a
      tag name. Such tags might now be prefixed with a <tt>tag:</tt> to enforce
      the command to take them as tag name instead of a UUID. For example:
      <verbatim>
        fossil tag add abcde $uuid
        :
        fossil update tag:abcde
      </verbatim>
      without the prefix <tt>tag:</tt> fossil would try to update to a UUID
      beginning with <tt>abcde</tt>. If no such UUID was found, fossil will complain
      and exit.