added support for untf in C_abline(), with test
added support for outer in C_axis(), with test
added support for grid.echo() on an expression (or call);  added support for grid.echo() into current grid viewport (rather than new page);  started help pages!
added prefix argument to grid.echo()
added support for type="n" to C_plotXY()
added support for par$family when drawing text;  added support for vfont in C_text();  added tests for both