Minor improvements to the msm tool

[theCalcaholic]

This pull requests adds two improvements to the msm command line tool.

1. msm list will now show which skills are already installed (issue show which skills are installed in msm list #1202)

2. A new msm info <skill> command has been added, with either being a distinct substring of a skill's name or the skill's github repository's url. It will display the readme.md from the repository in the terminal (if found). (issue Show skill description from within msm (command line) #1203)

[theCalcaholic]

Sorry for not referencing the issues in the commit messages. Next time I'll read the contribution guidelines before making the PR.

[forslund]

Thank you, this sounds like very useful features. I'll give it a go in a bit.

In the meantime I'd like you to sign the contributors licensing agreement (https://mycroft.ai/cla/), this is needed to make sure everything is Ok on the licensing side and you are aware what rights you're granting us.

[theCalcaholic]

Thanks for the information. I just signed the agreement. 👍

[LearnedVector]

This works really nicely. Tested and works for me. @forslund let me know if you have any concerns with this. otherwise it looks good to me. thanks @theCalcaholic!

[forslund]

I tested it earlier and it works really well. Merging. Big thanks @theCalcaholic!

[theCalcaholic]

I'm glad it works.

I think I should point out a short coming off the msm info command. It gets the information from the latest version's Readme instead of the version which is included in https://github.com/MycroftAI/mycroft-skills because I have no idea how to get the exact submodule version information without cloning the parent repository.

[forslund]

I think we still pull the head version so that's quite accurate. I'll make a note to check it over when we start to use the version the submodule is pointing to

[theCalcaholic]

@forslund Oh, perfect. Thanks!