kernel: Use the new auto-created sysctl ctx/tree in various drivers.

Everywhere where we formerly rolled a hw.fooX.* per-device ctx/tree
ourselves.

This commit switches it to dev.foo.X.*
dloader: First step in improving looks of boot menu

The boot menu essentially hasn't changed since it was converted to C
a few years ago.  The line between Fred and menu always bugged me, but I
suppose some people like it.  I added a new loader option called
"fred_separated" that is off by default, but if set on in loader.conf,
it will bring back the line.  When the line isn't present, Fred shifts
over by two characters which makes him centered.

While here, improve the colorization of Fred.  Colorization is not turned
on by default.  Before that can happen, adequate detection for a serial
console must be added to avoid using ansi color codes on it.

Since Fred has always been depicted as a red DragonFly with red wings, he
has been given bright red wings against a darker red body, and eyes have
changed from green yellow.  His shape has been tweaked as well.  His
scorpion stinger was sanded down to a small point and his mosquito beak
was made shorter so his head looks more like a DragonFly.  His thorax was
improved with curly brackets.

The original look can be restored by putting this in /boot/loader.conf:
  fred_separated="YES"

Approved by: Positive feedback on IRC channel