(Windows) main toolbar: added 'change text/param' button
(Windows) improved toolbar
Param. curve: editable now. Tooltips added to buttons
(Windows) designed dialog box for 2D param. curves
(Formulas - tiny detail...)
Param. curves: output ok
Param. curves: implemented picking, output (pb there)
Param. curves: more examples...
Param. curves: functions x(t) y(t) are parsed
Added %\paramcurvexy command, input and some display done so far