Improve get and comment descriptions

The “get” extended docstring had a formatting problem resulting in
‘user/vec1 and ‘user/map1 being called out as heading lines.
Apparently you can’t follow a bullet list with an indented code
fragment.

As for “comment”, I added new content.
fixed extended descr for get

Omitted a blank line.  Also made same change in 1.5 and 1.6.  (Are the
1.4 and 1.5 resources ever used?)
Merge branch 'master' into develop

Conflicts:
	resources/1.6.0/clojure.core/get/extended-docstring.md