* adds syscalls to use the partition location types
* no range implementation, helper file, refactorings
* more refactoring of syscall interface
* adds and refines trait
* improved documentation and partition_length function
* simplified ModRange
* cleanup
* new aligned_iter implementation
Removing support for writable flash regions permits to save 1 page in the binary
due to alignment constraints. It also permits to reduce the diff with libtock-rs
which doesn't support writable flash regions.
This commit also updates the `SyscallStorage` documentation.