add runx.sh

runx.sh starts Xephyr with a specific resolutaion and diplay number.
merge with borderalpha

Squashed commit of the following:

commit cc9ec2faeadacb4c0b5be501e7aa01b8d5c538f0
Author: Eon S. Jeon <esjeon@hyunmu.am>
Date:   Wed Oct 8 23:13:48 2014 +0900

    initial implementation
add brdalpha value to config.h