netlink: embed defragmentation into the Marshal class
gitignore update
iocore: remove obsoleted defragmentation code

The defragmentation logic was moved into the Marshal class
netlink: fix defragmentation
iproute: get_default_routes() shortcut
iocore: allow I/O broker to be a separate process
tests: add a test class to cover the forked I/O broker
iocore: return not so meaningless exception

When a command fails, it should return something useful
to debug the case -- beside of the fact of a failure.