change redirect config path with auto date move

This request intend to provide support for wiki farming, exactly change of conf file path 
so that each animal can hold own redirect hash table. Also resolve the issue #2.

The old hash data stored in the plugin directory (`redirect.conf`) will be copied to new file ''`redirect.local.conf`'' in DOKU_CONF directory, therefore no extra configuration required after the plugin update. This request is elaborated from #8

I propose to use `redirect.local.conf` for hash filename considering analogy with acronyms/entities etc.