builder: Handle trailing \ appropriately.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
builder: strip blank lines before processing any line continuations.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
The basics page moved, update link.

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Add a little info on how to talk to the TLS encrypted Docker Socket

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
builder: comments should also be elided in the middle of statements following a line continuation.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
builder: handle anything we cannot parse the command for as a fatal error.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #8580 from erikh/filter_comments_first

builder: strip blank lines before processing any line continuations.
Merge pull request #8583 from SvenDowideit/minimal-curl-command-to-tls-docker-socket

Add a little info on how to talk to the TLS encrypted Docker Socket
builder: provide a friendly message on parser errors

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #8582 from SvenDowideit/api-docs-link-to-basics-page

The basics page moved, update link.
Merge pull request #8579 from erikh/builder_html_panic

builder: handle anything we cannot parse the command for as a fatal error
Merge pull request #8578 from erikh/fix_slash

builder: Handle trailing \ appropriately.
Expanded release notes

Made it clear signed images is a preview feature and added a little more info about how the feature works.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Merge pull request #8595 from fredlf/signed-image-doco

Expanded release notes