Implement Single Channel Power Supply Interface

Adds an abstract single channel power supply object that wraps around an IPowerSupply. It can either be initialized manually (by passing IPowerSupply and channel number to the constructor) or by using EquipConf.

The syntax for equipment configuration files is as follows. The input-hw.json example has been updated.

"channels": {
  "first-channel-name" : {
    "hw-type": "PS",
    "device": "PS name from hardware block",
    "channel" : #,
    "program": {
      /* potential programming */
    }
  },
  "second-channel-name" : {
    "hw-type": "PS",
    "device": "PS name from hardware block",
    "channel" : #,
    "program": {
      /* potential programming */
    }
  }
}

A few other changes that are an effect of this:

• Remove some unused EquipConf member methods
• EquipConf::getPowerSupply now connects/checks the power supply on first fetch
• Rename hardware -> devices for the block where physical power supplies are declared