network: reorganize dnsmasq and radvd config file / startup

network: reorganize dnsmasq and radvd config file / startup

This patch splits the starting of dnsmasq and radvd into multiple
files, and adds new networkRefreshXX() and networkRestartXX()
functions for each. These new functions are currently commented out
because they won't be used until the next commit, and the compile options
require all static functions to be used.

networkRefreshXX() - rewrites any file-based config for dnsmasq/radvd,
and sends SIGHUP to the process to make it reread its config. If the
program isn't already running, it's just started.

networkRestartXX() - kills the given program, waits for it to exit
(see the comments in the function networkKillDaemon()), then calls
networkStartXX().

This commit is here mostly as a checkpoint to verify no change in
functional behavior after refactoring networkStartXX() functions to
fit in with these new functions.