Improvements to Logging of Mesh Converter

This MR contains some changes to the mesh converter tool. Most of them are cosmetic and change the way, logging output is presented. I added progress reports for reading and writing of all files, as sometimes this takes long - but it's weird to stare at a screen where nothing is happening for several (ten) seconds.

One feature changes is:

xdiv, ydiv and zdiv have been replaced by one parameter called divisions which takes either three or two components for the divisions in the individual dimentions:

divisions = 100 100 300

or for the 2D case:

divisions = 100 200

Which makes the configuration a bit easier.