Allow equations of the form "y = ..." for cartesians, "r = ..." for polars, etc (in addition to the "f(x) = ..." form).
- Which form to use by default is configurable. This is useful for e.g. a school environment, where the "y = ..." form might be preferred.
- The last used form is remembered as the default form.

svn path=/trunk/KDE/kdeedu/kmplot/; revision=565424