Numerous improvements
Numerous improvements

* Set package meta-data fields
* Specify config file location and external dependencies
* fpm options per build type
* Use uniq toor per build type, to reduce risk of cross-contaminating builds
* Added 'help' target
* Build version can now be overridden using PKG_REL

ryane/chronos-pkg,mesosphere/chronos-pkg,mesosphere/chronos-pkg