new type __yum_repo to manage yum repositories

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
++changes

Signed-off-by: Nico Schottelius <nico@bento.schottelius.org>
rename parameter repo_uri to uri as requested by nico
rename parameter service_uri to uri as requested
Merge branch 'bugfix_issue_327' of https://github.com/dheule/cdist
CentOS support for __hostname

Signed-off-by: Nico Schottelius <nico@bento.schottelius.org>
++releasedate

Signed-off-by: Nico Schottelius <nico@bento.schottelius.org>
implement --before and --after meta parameters as alternative to require=""

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
remove legacy code snippet: singleton object_ids have been removed in master

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
--whitespace

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
missing import

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
usable output on unresolved objects error

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
even nicer output

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
use pformat or even nicer output

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
bugfix: make --before actually work

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
update tests

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>
sanitize api for before/after relations

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>