Fix Lintian udev-rule-in-etc

Per the Rules, /etc is reserved for user-installed files.

http://lintian.debian.org/tags/udev-rule-in-etc.html
Merge pull request #274 from rtucker/dev-udev_rule_in_etc

udev: Fix Lintian udev-rule-in-etc error

While the default installation path for the udev rules are /etc/udev/rules.d, 
package maintainers should use the -DUDEV_RULES_PATH variable to specify an
alternative install location.