Fixes #28, param matrix bounds overrun

Adds three types of 3D arrays, the Vatrix (both dimensions vary), the MVatrix (variable columns, fixed rows), and the VMatrix (variable rows, fixed columns). These complement the Matrix (both dimensions fixed).

burnIter will now be automatically increased to 2x nParamsUsed if it is set too low. A warning message is printed.

nSave is set either to 100 or to 0.5 * burnIter.