Allow to work as a non-plugin

[kilpatty]

Currently hindexer only works as a plugin to HSD.

Ideally, this would be able to be run as an external service. I think the easiest way to transition the code to this is to move the "connect" blocks to a file that is only called if it's included as a plugin, otherwise we call the rpc methods and potentially listen to the HSD client via web sockets to add blocks.

Everything else can pretty much stay the same, we just have to change the "connection" code.