docs: misc. updates

[jorgeorpinel]

• Matches term: review "URL" term usage in remote cmds, and get/import-url dvc#4364 (rewrite sections and short descs. about URLs (remote, get/import-url))
• Review of term "feature(s)"
• Closes docs: insufficient description of params #1683
• Misc. copy edits

[shcheklein]

approving. there are some suggestions in the comments

[jorgeorpinel]

Sorry @shcheklein , I added more stuff to this PR before realizing you had already approved it. Please check once more. Won't add anything else.

[shcheklein]

Still a few unresolved issues here

[shcheklein]

let's do s3 example and can even explain about s3 prefix, or do another example if needed in a separate block?

[jorgeorpinel]

OK added S3 example before local example although I'm not sure it's needed as it's also in the S3 section. The S3 URL format is also explained in its section. See 3b7898e

[shcheklein]

looks good overall - some comments still to address, approving so that you can merge when you see it's done more or less