adds stable script to enable installation latest stable version
adds stable script to enable installation latest stable version

Signed-off-by: Kálmán Képes <82843f81ac5fbfe4bc7726b0ffdf0f626a90fffb@iaas.uni-stuttgart.de>

OpenTOSCA/install.opentosca.org,OpenTOSCA/install.opentosca.org