Add support for heat generation in bearings
A visiting PhD student is working on adding support for heat generation in bearings (and other elements), to serve as sources for heat transfer equations. At the moment, we documented the elements in module-fab-sbearings and strengthened the parsing of the input. The next steps will be to write the heat generation equations and make the value available as private data, to be used as an element drive caller in the source thermal element. We plan to work also on other elements. See the "thermo-bearing" branch for details.