Feature 1/merge cli config

[samuelvanderwaal]

Issue #1

Here's a first run at this. I create a cli.yml file and used clap to read config files as using structopt directly ends up with default values regardless of whether the user enters a CLI arg or not making it harder to do the manual merge. This works but I need some proper tests for it (I can do this as part of the integration tests for Issue #11) . If you don't like this approach feel free to reject PR and I can try something else.

[ThomasMeier]

@samuelvanderwaal I'll test this out today but I think this will work fine. If structopt is unneeded do you need to remove the structopt crate and comments?

[samuelvanderwaal]

structopt is still used in this implementation. clap is used to check the occurrences of each possible cli argument and overwrite values in the structopt instance before that gets passed to factom_service::run. This keeps most of your code and just adds one extra function for checking what cli args were actually submitted by the user.