added option to --restore an existing mlaunch configuration.
added option to --restore an existing mlaunch configuration.

Each start writes a config file to the data directory, called .mlaunch_startup
if --restore is present, mlaunch will read it and re-create the same configuration
of nodes.

parkhyeonghwa/mtools,ces0712/mtools,aerrami/mtools,devkev/mtools,rueckstiess/mtools,devkev/mtools,aerrami/mtools,gormanb/mtools,tomzhang/mtools,tomzhang/mtools,devkev/mtools,gormanb/mtools,yaowenqiang/mtools,tomzhang/mtools,yaowenqiang/mtools,gormanb/mtools,parkhyeonghwa/mtools,corymintz/mtools,parkhyeonghwa/mtools,yaowenqiang/mtools,ces0712/mtools,rueckstiess/mtools,corymintz/mtools,aerrami/mtools,corymintz/mtools,ces0712/mtools