Update signing key in Development Environment Docs
Split out Why_Git from Getting_Started
panic_simple shouldn't have any reference to typed_data.h
update Development Environment instructions

- change msp430 toolchain to msp430-46
- change repository key to Eric Decker
shimmer/span: add port drive defines
Merge branch 'tp-master' of https://github.com/tp-freeforall/prod into tp-master-andres