Add tag to metadata, allow for build scripts to be more configurable, modifications for Ubuntu 14.04

build_scripts/run_centos.sh: Make IMAGE_VERSION, AUTHOR, EMAIL configurable via environment, add tag to metadata
build_scripts/run_ubuntu.sh: idem, switch to Ubuntu 14.04
ubuntu/ubuntu_stratus.preseed: Patch with diff to ubuntu/ubuntu12_stratus.preseed in 60a2ed206013569f46c46359a556f613814717f1 (from ee0ce4bb016949221c63c01e95371f133c48e0bb)