Probe Functionality

Purpose

Introducing the functionality to probe points on MeshSeries. This feature was previously available for PVDs via VTUInterface. Now we have it generalized for both PVD and XDMF/HDF5. Also added a plot_probe function which uses this in a preformatted setting. For now for both formats return numpy arrays, but I may add the option in the future to use the same dict typing as in VTUInterface. Further, some tests for meshlib were added.

Commit-wise review recommended