* CMake integration, no autotiools
* alignment panel is now correctly renamed to setting panel
* source view is now correctly renamed to code view
* Merge FLTK FLUID docs into FLUID user manual.
* Add two simple entry tutorials
* Remove FLUID chapter form FLTK docs.
* GitHub action to generate HTML and PDF docs and
make the available as artefacts
* this commit introduces a few FIXMEs and TODOs that probably
can't be solved until we do some major refactoring. They work for
now, but adding more layout controlling widgets will be hard.
also added and fixed a few comments
STR 3210: fixed indenting of widget callbacks.
Also fixed what is considered a 'name' (could still be improved).
Also better formatting inlined functions in the header.