Feature/battery monitor adc

[elsalahy]

Summary:

Adds support for battery and system internal voltage reporting Closes #29

Changes:

• Adds a library of battery monitoring APIs
• Adds a basic app battery reporting

Notes for Reviewers:

Tested and looks good.

Release Notes: (optional)

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[elsalahy]

@azerimaker this is a great test, thanks a lot for confirming the functionality