Implement methods for adding and removing host configurations

[rbywater]

This commit adds the ability to programatically add and remove host
configurations.

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[eddyhub]

Hi, I was wondering if anyone had a chance to take a look at this? Is there a chance this commit will be merged any time soon?

[rbywater]

I've asked on the mailing list a while back and got no response. So, unless someone else jumps in first, I'll look at doing at merging this PR and doing a new release soon myself.

[eddyhub]

I need this commit for a puppet module and was about to add the necessary methods myself but a check of the pull requests revealed, that you already did the necessary changes. So if I can help getting the changes to a new release just tell me.

[rbywater]

Just released 1.13 so hopefully that will flow through soon with this change in. (Note I had a few issues so hopefully it does come through properly!)