Fix zoom icons, add Lower/Upper bound icons to Gantt Chart

[GoogleCodeExporter]

- zoom in/out icons are currently not dsplayed with gantt chart (only tiny
buttons can be seen in bottom-left corner. icons are already in jar, this
is probably just a matter of providing the right resource path so that the
icons are loaded correctly

- gantt chart currently displays only lower bounds for start and end times
for all activities. new buttons should be provided so that the user can
switch the view from lower bound to upper bound.

Original issue reported on code.google.com by Matthew....@gmail.com on 30 Sep 2009 at 6:34