Move lots of general docs to webpage

[apeltzer]

As @ewels was so nice to add the super easy possibility to shift over some of the markdown basic documentation from tools, I took the liberty to start doing this now 👍 I might add some more docs there, and we need to remove (once this is merged) the rest of it in the tools repository to have only one location in the future.

Once the syncing kicks in after the next tools release, we can simply link to the main webpage / documentation there and should be up2date 🎉

[apeltzer]

x-ref: nf-core/tools#298, which removes these docs from nf-core/tools

[apeltzer]

Updating the Troubleshooting section is also something that I'd like to do soonish, but that is something for the hackathon next week 👍

#94

[ewels]

Looking good! A few comments about content, though I realise that this is mostly copying and pasting, so no worries if you'd rather merge now and refine later.

I do think that there is quite a lot of duplication in these docs, and that they're not particularly well organised. I think that we could do with a general overhaul of it all pretty soon...

[apeltzer]

Yes, I also think we need to merge certain parts of this and also make these updates everywhere across all pipelines available in linking to this over here 👍
Will merge now that I changed all your requests + added some more disclaimers, can later polish this even further (as its also now independent of nf-core/tools template, once that PR is merged too!)