fixed anyconfig.Bunch.update_w_merge(..., merge_lists=True) to process cases if former Bunch objects have keys of which values are list not presented in the later Bunch objects while merging series of Bunch objects
enhanced test cases to catch cases noted in the previous commits
added anyconfig.backend.backends.list_types method to list supported config types
added test cases for anyconfig.backend.backends.list_types()
exported list_types
changed anyconfig.api.{multi_,}load to allow multi_load accepting both list of paths and its glob pattern
added some more test cases for anyconfig.api.multi_load
fixed some grave bugs and made it work