fix yum_rpm package method so that specifying arch is possible

package_list_command is changed so that the output is similar to that
of 'yum list installed', and the regular expressions that use this
output are simply copied from the yum package method. The allmatches
option to rpm with package_delete_command is removed.
Merge pull request #419 from trondham/master

cfengine_stdlib.cf: fix yum_rpm package method so that specifying arch is possible