Thanks to Eric Monson for the suggested patch, setting the field and
content type - this should address the issues outlined in that report.

Removed pointless stored variables, and adapted to deal with the more
general case of axes assuming only perpendicular axes in x and y.

This should give better defaults when adding points plots, adjusting the
default back to what it was in line plots.

The clang frontend is stricter about the declaration of functions
before use, this should hopefully fix up the compilation errors reported
in the bug report.

Backward integration was failing due to missing a negative
sign when setting the time step.

Check the endIndex instead of just searching for parenthesis indefinately in a while loop.