(core): index of services
Description
New becomers often complain about the lack of clean index of services.
Proposal
We should provide a nice index of services, at least the most used in a first time. They should be sorted by category. Doing this manually could be tedious. Since we follow a nice doxygen convention now, it is probably possible to generate this. Either with a python script, or maybe it is possible to use Sphinx to this end. Doxygen could also be an alternative but this might be harder.