Update scda error management

[tim-griesbach]

Update scda error management

Proposed changes: Change the scda error management and the corresponding documentation. In concrete terms, this means

• write a general error management paragraph in the doxygen documentation,
• add the API of the function sc_scda_ferror_class and
• introduce the struct sc_scda_ferror_t and document its semantic.

[cburstedde]

Cool thanks!