Add speaker, president and deputy president to whipless parties

You should never see any of these except for speaker and as they only
provide a casting vote on a tiebreaker we shouldn't show them as
having a whip
Fail if the user enters a blank title. Fixes #124
Make database field bigger to accommodate large default motion text

Because some default motion text is huge we embiggened the size of the
pwdivision.motion field in aa6229f9bfbf9aceb09cf411cd3ca94287bd4df9.

When you edit a division the whole motion text starts to get saved in
pw_dyn_wiki_motion.text_body so it needs to be bigger to save the
entire default text, e.g. when you only edit the title (fixes #125).