Add missing blank lines in between list items

Lists with paragraphs as items need blank lines in between
items to generate correct layout.

Docker-DCO-1.1-Signed-off-by: Lance Chen <cyen0312@gmail.com> (github: Lance0312)
Merge pull request #5323 from Lance0312/docs-missing-blank-lines

Merged.
Freeze server/server.go for deprecation

* Add notice in server/server.go explaining not to add stuff there, and
what to do instead.

* Make myself a sole maintainer of server/ to avoid concurrent edits
while refactoring.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Merge pull request #5334 from shykes/freeze-server

Freeze server/server.go for deprecation