set host mac of client_mock to another host

- send one empty request to host to get current time (have to do this since we power cycle the CAM every time we use it)
- name picture according to the current date and time

defined pin numbers for managing data transmissions of I2C, SDI12, RS485.
initial setup for the client_central_mast client

- move get_host_mac to RtcMemory implementation
- allow hardcoding of mac address of host on client

minor refactors