rename config submodules for consistency
update holland.core.util.pycompat

- deprecated features available in python2.6+
  (re.Scanner, string.Template, namedtuple)
- added backport of python2.7's collections.OrderedDict
- added backport of python3.2's functools.lru_cache
- added backport of python3.2's functools.total_ordering
update holland.core to use new pycompat implementations
remove holland.core.util.datastructures
remove tests for fuctionality removed from pycompat
Merge branch 'amsterdam' into refactor_config_api
export pycompat implemenations from holland.core.util
Merge branch 'amsterdam' into refactor_config_api
backport move_to_end method from py32 OrderedDict
cleanup Config api
reference Config.section rather than Config.name in Configspec
config.insert is not a valid method
add is_alias property to Check
update Check properties to use itemgetter

previously this was using a lamba for support for old
python versions, but this is much cleaner in any vaguely
recent python, especially in python2.6+ which is now required
update module docstring in config.checks
fix import path for holland config tests
configspec bugfixes
use @plugin_registry.register to register validators
ensure RegistryPluginLoader instantiates the plugin class
lazy load configspec to break an import cycle