New implementation of the FrontEnd and FrontEndCfg classes

This MR does a basic cleanup of the FrontEnd and FrontEndCfg classes to decouple the inter-dependence of the chip connectivity parameters. This is done by creating a new class "FrontEndConnectivity" which has the important parameters (txChannel, rxChannel and lockCfg) with the appropriate constructors to retrieve them. The FrontEndCfg class, which stores the information about other chip configuration registers, now inherits from the FrontEndConnectivity class. Finally, the "init()" of FrontEnd class now takes the FrontEndConnectivity config as the parameter and calls its constructor to set the channels automatically. This is done to easily extend channels in the future (for e.g. adding the register rx channel) simply in the FrontEndConnectivity class without changing the implementation in the FrontEnd or FrontEndCfg classes. The constructor and init() implementation of the various FEs, inheriting from FrontEnd class, are also modified accordingly.