Allow multiple RF modules simulatenously

[melyux]

Description:

So this is how I've been successfully using the Pilight and RF modules simultaneously on the same OMG installation. I have a normal RXB6 receiver, and its same data pin goes to 2 different pins on the ESP8266 (presumably to take advantage of the hardware interrupts thereof).

The code change is dead simple: just enable all the RF modules you want instead of only enabling one.

I use a bitfield for setting the active receiver (0000), so you can set multiple receivers at the same time with e.g. 0011, meaning {"active": 3} for Pilight + RF.

There are obviously some things that might not work that I haven't tried, like CC1101 using Pilight + RF or HA discovery, but I'm just a simple man, I use the old fashioned RXB6 variants for most OOK things like this. The code will need adjustment and sanity checks like this. Since I'm not sure how you'd want to implement configurations and etc, this is a draft, but it works perfectly for my purposes, so I wanted to share it in hopes of getting a variation of it merged for others' benefit. (see #450)

Thanks @1technophile for your efforts and openminded kindness through the years.

Checklist:

• The pull request is done against the latest development branch
• Only one feature/fix was added per PR and the code change compiles without warnings
• I accept the DCO.