ref-manual: Created form for context images for variables

Fixes [YOCTO #6158]

Updated the style scheet file to format glossary variables in
such a way to allow for a PNG file of standard size to be
displayed below each variable.  Right now, the PNG file is a
generic placeholder.  Each variable displays a PNG file.

Updated each variable to include that PNG file.

(From yocto-docs rev: 24b7b847b7093022a49a014395df0c3a8c019331)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-style.css

@@ -201,8 +201,17 @@ div.variablelist dl {
 .variablelist dl dt,
 .variablelist dl dt span.term {
   font-weight: normal;
-  width: 20em;
+  width: 0em;
   text-align: right;
+  margin-top: 4em;
+  margin-left: .5em;
+  margin-bottom: 0em;
+    -webkit-column-count: 2; /* Chrome, Safari, Opera */
+    -moz-column-count: 2; /* Firefox */
+    column-count: 2;
+    -webkit-column-gap: 4px; /* Chrome, Safari, Opera */
+    -moz-column-gap: 4px; /* Firefox */
+    column-gap: 4px;
 }
 
 .variablelist dl dt {
@@ -211,8 +220,8 @@ div.variablelist dl {
 
 .glossary dl dd,
 .variablelist dl dd {
-  margin-top: -1em;
-  margin-left: 25.5em;
+  margin-top: -3.5em;
+  margin-left: 15.5em;
 }
 
 .glossary dd p,