Remove remnants of OpenChannel rpc

[JssDWt]

The OpenChannel rpc is removed in #178. Remove remaining remnants of the OpenChannel rpc in config, code, and other rpcs.

config.go:

• PublicChannelAmount. (no need to increment the channel capacity anymore here?)

  lspd/interceptor/intercept_handler.go

  Lines 352 to 354 in 81019b0

  	if capacity == i.config.PublicChannelAmount {
  	capacity++
  	}

lspd.proto
ChannelInformationReply

• channel_capacity. Check client implementations (breezmobile, sdk) whether it's safe to remove.
• target_conf? Is this necessary at all? It doesn't mean anything in the 0-conf channel context, because there is no promise channels will be confirmed within a certain amount of blocks.