Urgent structural changes to IPowerSupply

These are few changes to IPowerSupply that are urgently needed, and block many other developments

• clarify what connect and initialise do - add comments
• add function program() - to be called by initialise that can be used to set-up the PS (and so it reads a specific block in the json file)
• modify turnOn() function to identify the channel directly from json file
• have a pointer to serialCom in IPowerSupply
• get rid of autoconfig for the moment

These changes also need appropriate changes to the Rigol class832 class, that is the only one that is currently inheriting from IPowerSupply

To be developed in a branch, starting from devel