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

cmd/sas_switch_id/Makefile.am

@@ -1 +1 @@
-dist_bin_SCRIPTS = sas_switch_id
+dist_udev_SCRIPTS = sas_switch_id

cmd/zpool_id/Makefile.am

@@ -1 +1 @@
-dist_bin_SCRIPTS = zpool_id
+dist_udev_SCRIPTS = zpool_id

cmd/zvol_id/Makefile.am

@@ -4,7 +4,7 @@ DEFAULT_INCLUDES += \
 	-I$(top_srcdir)/include \
 	-I$(top_srcdir)/lib/libspl/include
 
-bin_PROGRAMS = zvol_id
+udev_PROGRAMS = zvol_id
 
 zvol_id_SOURCES = \
 	$(top_srcdir)/cmd/zvol_id/zvol_id_main.c