feat: AVR Compatibility

[zfields]

This modifies the implementation to be compatible with avr-gcc, which can then be supported by the Notecard.

The core change is to templatize the implementation on CloudInt.

This allows the library to accept all sizes and signed-ness of integers without requiring multiple implementations (e.g. CloudInt, CloudUnsignedInt, etc...). Several cascading changes are then required to accommodate this main change.

Other changes include pulling in ArduinoSTL for std::list support, and migrating lambda expressions to static functions.