CI was not building the a.rs application due to the requirement of b.bin
having been built first. Add a feature flag to examples so that CI can
build them including a dummy application.
Update a.rs application examples so that they compile again.
* Add nRF91 as target in CI builds
* Add example linker scripts for nrf91
* Make less nRF52 assumptions example config
* Add llvm-tools-preview required for cargo objcopy example
Obtaining the current WDT config is important so that we do not have to duplication configuration around the place. A constructor method has been introduced that returns WDT config in accordance with how the register is presently configured. The bootloader example has also been updated to show the watchdog can be obtained and used.
* Remove the need for generic const expressions and use buffers provided in the flash config.
* Extend embedded-storage traits to simplify generics.
* Document all public APIs
* Add toplevel README
* Expose AlignedBuffer type for convenience.
* Update examples
