Add parameter normalization utility functions in JXG.Expect

JXG.Expect provides methods for normalizing parameters, e.g. a function
that requires coordinate values for its calculation can use JXG.Expect.coordsArray()
to normalize the user input (JXG.Point, JXG.Coords, and coordinate arrays)
into coordinate arrays.

This module will be extended to provide geometric normalization as well, e.g.
the user gives coordinate arrays (containing numbers or functions) or points
and gets a point element in return to create a line or a sector element.
Use the stdform when calculating the angle of a line
Add algorithms to determine the convex hull of a set of points and its area.

The algorithm used is known as Graham's Scan, available via GrahamScan in the
math/geometry module. Calculation of the signed area of a triangle and a
general non-self-intersecting polygon is also added to this module.