Various small docs improvements

[gundalow]

Firstly thanks for this great bit of Software, I just got it setup over the weekend (in Digital Ocean). I'm no programmer, though I hope these docs improvements are useful. If I've done too much let me know and I can trim it down a bit.

1. Use consistent terms for Docker installs
2. State requirements for installs
3. Don't repeat basic Docker setup (should help avoid pages getting out of sync in the future
4. Few minor formatting/spelling improvements
5. Tweak formatting of the upgrade guide to hopefully make it clearer

[adriankumpf]

These improvements are really useful. I wasn't sure at first if the basic Docker setup should be removed from the readme, but it definitely makes sense to have the instructions in one place. Thank you!

[gundalow]

@adriankumpf Thank you for the prompt review and merge.
I was also in two minds about the install doc, glad what I've done works for you.

Anything else I can help with? I'm a maintainer for some major projects on GitHub, so I know my way around a fair bit of stuff.

[adriankumpf]

Anything else I can help with? I'm a maintainer for some major projects on GitHub, so I know my way around a fair bit of stuff.

Wow! Yeah, there are a couple of things :-) I would be very happy if you could proofread the rest of the documentation or the web interface (labels, tooltips etc) . Some parts probably don't make much sense or sound strange to a native speaker. Answering questions and generally helping with GitHub issues would also be awesome. In addition, of course, contributions of any kind are very welcome – e.g. if you're familiar with Grafana feel free to improve the dashboards or add new ones.