Only allow one active glucose data source

[bharat]

Separate CGM sources out into their own section and enforce zero or one
active sources at any given time. This requires a new boolean value to
track whether the G5 transmitter is enabled independently of the actual
transmitter ID.

While we're at it, create a separate config section for the pump to
group it with the pump battery type since those are not really
configuration values and go together.

[bharat]

This resolves #361 and makes room for us to add Enlite in #349

[bharat]

Some notes:

1. Enabling G5 shows the transmitter ID row (it animates out)
2. Enabling either G4 or G5 disables the other one
3. Disabling G5 (either directly, or by enabling G4) hides the transmitter ID row
4. Moved pump id and battery chemistry into their own section
5. handle the upgrade case (now transmitter enabled is explicit, not implicitly dependent on having a well-formed transmitter id)

[loudnate]

s/Cgm/CGM

[bharat]

pull request am i
quietly i languish here
save me, @ps2

[ps2]

This looks good to me. Are there parts of the guide that should be updated?

[Kdisimone]

I can do this. Just updating Anna's app now. This went into dev branch though...so I will note that in guide and when it goes to master I'll update the guide for that too.