Documentation improvements

Doc improvements for 1.0.

Improve link and alt image text. Closes #709 (closed) and #699 (closed) .

Remove conversations for action concept (has never been added to the spec formally), closes #601 (closed) .

Clarify Intent and Commitment gray area, closes #662 (closed) .

Fixes to all example yaml for spec changes, closes #713 (closed) . Except it should be all run through a yaml validator; and we need to fix the git.io context issue.