Restructure C++ Classes in order to reflect SilecsClasses

• each PLC has silecsClasses
• each Device holds a link to it's silecsClass
• each Device has Blocks
• each Block has Registers It should be possible to run recv/send for all devices of a class at once (per Block) --> static method at device-level ?

In old impl. Block was not device-specific !! Thats a huge Bug !! ( SilecsPLC.cpp:533 of v0.10.0 )