4) Introduce conversion profiles for the reflow

There are roughly 50 paramateres steering the heuristics of the detection of layouts.
These parameters can not be optimized for all layouts at the same time and currently represent "the best average result".
E.g. justified text can be better detected with settings that on the other hand will not detect small data-tables very well.
To improve the reflow/rendering of documents of certain types, baselines for conversations are introduced.

These will be:

"average" (current state), 
"dense" (for data-tables & layouts with dense columns), 
"spacious" (when having sufficient whitespace between elements)
"custom" (with the option to tweak individual parameters for developers)

Screens: see https://confluence.translate5.net/spaces/MI/pages/689602561/Visual+Enhancemets+IV