Move udev rules from /etc/udev to /lib/udev

This change moves the default install location for the zfs udev
rules from /etc/udev/ to /lib/udev/.  The correct convention is
for rules provided by a package to be installed in /lib/udev/.
The /etc/udev/ directory is reserved for custom rules or local
overrides.

Additionally, this patch cleans up some abuse of the bindir install
location by adding a udevdir and udevruledir install directories.
This allows us to revert to the default bin install location.  The
udev install directories can be set with the following new options.

  --with-udevdir=DIR      install udev helpers [EPREFIX/lib/udev]
  --with-udevruledir=DIR  install udev rules [UDEVDIR/rules.d]

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #356