TransmitProfiles JSON PowerSource enumeration is incomplete

[larvacea]

In master, the std::map transmitProfilePowerState used to map JSON string to PowerSource enum values does not have any string that maps to PowerSource_LowBattery.

On Android, you may enjoy one side effect of this by running the SDK on the emulator in a low-battery state. Since no other rule matches PowerSource_LowBattery, TPM will select the default rule and shut down transmission.

In addition it may be worth revising the default profiles to include this state if we do not intend to shut down telemetry for low battery, or alternatively document this behavior (after all, it may be desirable to shut down HTTP transmission when the battery is low).