MDL-55168 css: ignore some stylelint complains

1) Legacy css where it would not be a good use of time to
   update.

2) Ignored some long lines and added todo

3) Fixed some line length issues

mod/assign/styles.css

@@ -1,3 +1,5 @@
+/* stylelint-disable max-line-length */
+/* FIXME: MDL-55370: remove this stylelint disable */
 .path-mod-assign div.gradingnavigation div {
     float: left;
     margin-left: 2em;

mod/book/tool/print/print.css

@@ -1,4 +1,3 @@
-/*csslint important:false */
 #page-mod-book-print {
     color: #000;
     background-color: #fff;
@@ -142,6 +141,6 @@
 
 @media print {
     .hidden-print {
-        display: none !important;
+        display: none !important; /* stylelint-disable-line declaration-no-important */
     }
 }

mod/scorm/styles.css

@@ -240,7 +240,7 @@
 #page-mod-scorm-player #scormpage div.yui3-u-1-5,
 #page-mod-scorm-player #scormpage div.yui3-u-1-24 {
     display: inline-block;
-    *display: inline;
+    *display: inline; /* stylelint-disable-line */
     zoom: 1;
     letter-spacing: normal;
     word-spacing: normal;