Add support for buwizz 2

[Hilbert70]

This request add support for the BuWizz 2 only (we only have that version).

It also adds configurable powerlevel:

   {
      "address": 2,
      "name": "Buwizz2 loco",
      "bleHubs": [
        {
          "type": "BuWizz2",
          "address": "50:xx:xx:xx:xx:xx",
          "powerlevel" : "normal",
          "channels": [
            {
              "channel": "A",
              "attachedDevice": "motor"
            },
            {
              "channel": "B",
              "attachedDevice": "motor",
              "direction": "reverse"
            }
          ]
        }
      ]
    }  

It can have the following values:

"disabled"
"slow"
"normal"
"fast"
"ldcrs"

These are case sensitive and are only used by the BuWizz 2 hub, the other hubs ignore this value.

[Mattzobricks]

Tested it with a relatively complex scenario (2 BuWizz2 units, 4 motors, 2 PF lights). All works as expected. Nice job, @Hilbert70!