Added
* extra argument `pkg_hash_required` for `Repository` command
* support for version limitation of `Install` and `Uninstall` requests
  in package name (such as `foo (>= 1.0.0)`).

Changed
* Execution is now terminated when there is no hash for package being
  installed in repository index unless `pkg_hash_required` is set to
  `false` for that repository.

Removed
* Extra option `version` for `Install` request. You should append
  version specifier to package name the same way as it is done for
  dependencies.

Fixed
* `ROOT_DIR` not being defined for `hook_postinst` and
  `hook_reboot_required` on replan execution.