Change SettingsHandler to take a buffer instead of assuming that the
setting file to read is always on the host filesystem for more
flexibility and make it possible to use the new filesystem interface.
Must be 9 characters at most; otherwise the serial number will be
rejected by SDK libraries, as there is a check to ensure the string
length is strictly lower than 10.
This moves all the byte swapping utilities into a header named Swap.h.
A dedicated header is much more preferable here due to the size of the
code itself. In general usage throughout the codebase, CommonFuncs.h was
generally only included for these functions anyway. These being in their
own header avoids dumping the lesser used utilities into scope. As well
as providing a localized area for more utilities related to byte
swapping in the future (should they be needed). This also makes it nicer
to identify which files depend on the byte swapping utilities in
particular.
Since this is a completely new header, moving the code uncovered a few
indirect includes, as well as making some other inclusions unnecessary.
