bump api to 1.14 & update docs

Docker-DCO-1.1-Signed-off-by: Adrien Folie <folie.adrien@gmail.com> (github: folieadrien)
Clarified TLS Docs

Made a "Secure by default" section, create 2048-bit keys, various cleanups.

Docker-DCO-1.1-Signed-off-by: Aaron Huslage <huslage@gmail.com> (github: huslage)
Merge pull request #6890 from huslage/tls-doc-fixes2

Clarification of TLS Docs
Use container.Lock in public ToDisk method

Here was possible race with inspect where we changing HostConfig.Links
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Merge pull request #6979 from LK4D4/fix_race_inspect_start

Use container.Lock in public ToDisk method
proper rebase

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6985 from vieux/fix_api_1.14

bump api to 1.14 & update docs