luci-app-dnscrypt-proxy: new package

to ease the dnscrypt-proxy configuration I've build this package,
main features:
* full resolver list handling, incl. list refresh and
  simple resolver selection per instance
* trigger support
* support the following (conditional) options:
  * resolvers_list
  * ephemeral_keys
  * blacklist
  * block_ipv6
  * local_cache
  * query_log_file

Signed-off-by: Dirk Brenken <dev@brenken.org>