MDL-55452 stylelint: prevent use of !important

Don't try and fix existing issues, just prevent new ones landing..

.stylelintrc

@@ -31,6 +31,7 @@
         "declaration-colon-newline-after": "always-multi-line",
         "declaration-colon-space-after": "always-single-line",
         "declaration-colon-space-before": "never",
+        "declaration-no-important": true,
         "function-calc-no-unspaced-operator": true,
         "function-comma-newline-after": "always-multi-line",
         "function-comma-space-after": "always-single-line",

theme/bootstrapbase/less/moodle/course.less

@@ -850,7 +850,8 @@ span.editinstructions {
     }
     .moodle-actionmenu {
         .iconsmall {
-            max-width: none !important; /** reset sets 100% !important which breaks on IE8 without this !important */
+            /** reset sets 100% !important which breaks on IE8 without this !important */
+            max-width: none !important; /* stylelint-disable-line declaration-no-important */
             width: 16px;
             height: 16px;
             padding: 4px;

theme/bootstrapbase/less/moodle/expendable.less

+/* stylelint-disable declaration-no-important */
 table#explaincaps,
 table#defineroletable,
 table.grading-report,

theme/bootstrapbase/less/moodle/filemanager.less

+/* stylelint-disable declaration-no-important */
 // File Picker and File Manager
 .filemanager,
 .filepicker,

theme/bootstrapbase/less/moodle/modules.less

@@ -136,7 +136,7 @@ select {
 
 // Override hardcoded forum modules styling
 .forumsearch input[type=text] {
-    margin-bottom: 0 !important;
+    margin-bottom: 0 !important; /* stylelint-disable-line declaration-no-important */
 }
 
 #page-mod-forum-discuss .discussioncontrols {

theme/bootstrapbase/less/moodle/responsive.less

@@ -397,8 +397,10 @@
         padding-right: 10px;
     }
     #helppopupbox {
+        /* stylelint-disable declaration-no-important */
         width: auto !important;
         left: 0 !important;
+        /* stylelint-enable declaration-no-important */
     }
 }
 // Shrink calender when short on space in block

theme/bootstrapbase/less/moodle/undo.less

@@ -69,10 +69,9 @@ li.section.hidden,
  * basically if you see things shifted left or right compared
  * with where they should be check for a .row
  */
-
 #turnitintool_style .row,
 .forumpost .row {
-    margin-left: 0 !important;
+    margin-left: 0 !important; /* stylelint-disable-line declaration-no-important */
     // not sure if this needs !important
 }
 #turnitintool_style .row:before,