implicit assumptions madness and support turning axes on and off
(suggested by Time Tuominen in issue 466), this adds axis.show and
axis.reserveSpace - still need to figure out what to do about the
public axis-snarfing API and get it documented.


git-svn-id: https://flot.googlecode.com/svn/trunk@302 1e0a6537-2640-0410-bfb7-f154510ff394