modularizing BangleJS

One thing i wanted but couldn't figure out was a way to have just a Bangle_driver_impl.h without a Bangle_driver_impl.C

I wanted this because the file mainly includes empty weak functions file because the whole point is to give the project a place to inject hardware specific code. But because the each bangle_device_driver_impl.c includes the headers of the Bangle_driver_impl.h you can't have the weak pointer definition because then you'll get double declarations error.