Break! Rename vmm_config to VmmTblAPI. Remove pFEN

vmm_config is now called VmmTblAPI. Following [Loki's example](https://gitlab.esss.lu.se/nice/dev-epics-modules/fe-r5560-loki/-/blob/include-api-on-module/r5560LokiApp/src/r5560LokiApi.h?ref_type=heads)
it inherits from RMM API's FrontEndBase, which means it doesn't need
pFEN as a class parameter anymore.

This breaks the whole application compilation, but it was already broken
in the new API structure.

It you compile only with

SOURCES += $(APPSRC)/VmmTblAPI.cpp

in the Makefile, it works. My intention is to keep adding the other
files now.