Add udev rules and scripts for demo platform configuration

Add recipes for udev rules and associated scripts
1) Support USB attached I2C devices for RTC and HVAC LED support.
   The RTC support loads and configures the required rtc-ds1307
   driver, and sets the time from the RTC clock.  The HVAC LED
   support configures the LED device names for use by the HVAC
   binding.

The new demo-i2c-udev-conf recipe is
added to DEMO_PLATFORM_CONF variable in packagegroup-agl-demo-platform
to have them added to the agl-demo-platform image.  Since they use
udev rules to detect the corresponding hardware, this should be safe
for all platforms.

Change-Id: Id08571b43c7ae9275496980e0a5568e145a1f653
Signed-off-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>