release-notes: add straggler jira items, spelling

Added a few last Jira items fixed today for the 1.7 release and
fixed spelling errors found in Jira titles. Added links to
samples/boards from reviewer comment.  Fixed typo in 1.6 release
notes section.

Change-Id: Ibb97f99592db6f7739a2a0148f5e898674fe5d01
Signed-off-by: David B. Kinder <david.b.kinder@intel.com>