Add support for comments in hiera-eyaml-gpg.recipients file

[tampakrap]

This commit adds support for comments in the abovementioned file, so that we do something like the following:

user1@example.com

0x12345678

user2@example.com

0x12348765

[sihil]

In my recipient files I typically refer to the keys by e-mail address (UID) anyway - which works well and is self-documenting. Having said that, I can see some use cases for hardcoding key IDs and so am happy to merge this.

[sihil]

Thanks for contributing @tampakrap!