Clean up obsolete test(1) usage - don't use -o, use sh || instead.

This one was particularly bad:

if [ -z ${dev} -o ${junk} ]; then

was supposed to be validating an entry read from a config file,
dev should be not empty, and junk should be empty (ie: correct
number of fields present). If that test succeeds, the line is
bad, and we error out.

But if dev was empty, and junk was also empty, that turned into

if [ -z -o ]; then

which tests if "-o" is the empty string, which it isn't, so instead
of succeeding, and considering the entry invalid (no dev specified)
the code would just carry on as if all was good.

Because of this, a bunch of quoting fixes were also made (there might
perhaps be more needed).

Use rcvar=$name syntax consistently in rc.d scripts which makes it easier to
search for rc.d scripts where rcvar differs from name. No functional change.

provide a new 'bluetooth' rc.d script, to handle Bluetooth configuration
in a simpler manner. This replaces btattach, btconfig, bthcid, btdevctl
and sdpd scripts, and also should not require any configuration settings
other than "bluetooth=YES", though the full range of configurations is
still possible.