The libxmlb library is much faster to query, and does not require the daemon
to parse the XML metadata at startup. It's a zero-copy mmap design that is more
modern and less clunky.
RSS has reduced from 3Mb (peak 3.61Mb) to 1Mb (peak 1.07Mb) and the startup
time has gone from 280ms to 250ms.
This was a mistake originally for two reasons:
* The only device to use ELF as a deliverable is the altos devices
* ELF has nothing to do with the DFU specification
This moves the code to where it belongs.
