Substituted assert using exception. Added docu.

Using std::invalid_argument exception instead of assert leads to
error messages both in release and debug version.
Added exception to handle invalid input and docu.

Added exception std::invalid_argument to constructor of class template TemplateVec.
Made documentation more specific.
Test PointVec with empty input.
Explicit FAIL in PointVec test with empty input.

Cause testrunner to stop otherwise.
Test PointVec constructor with single point input.
Test PointVec with nullptr input.
Explicit FAIL in PointVec test with nullptr.
Test PointVec with two diff input points.
Explicit FAIL in PointVec test with two points.
Allocate vecto of points. New tests.
Extract method points_equal() query.