Move common scss mixins to common/static/sass, and tweak the video player to have more in common between the cms and the lms

cms/static/sass/_mixins.scss

@@ -0,0 +1 @@
+../../../common/static/sass/_mixins.scss

cms/static/sass/base-style.scss

@@ -3,6 +3,7 @@
 @import 'keyframes';
 
 @import 'reset';
+@import 'mixins';
 @import 'base', 'layout', 'content-types';
 @import 'calendar';
 @import 'section', 'unit', 'index';

common/lib/xmodule/xmodule/css/video/display.scss

@@ -5,6 +5,7 @@ div.video {
   margin: 0 -12px;
   padding: 12px;
   border-radius: 5px;
+  font-size: 16px;
 
   article.video-wrapper {
     float: left;

common/static/sass/_mixins.scss

@@ -0,0 +1,24 @@
+@function em($pxval, $base: 16) {
+  @return #{$pxval / $base}em;
+}
+
+// Line-height
+@function lh($amount: 1) {
+  @return $body-line-height * $amount;
+}
+
+@mixin hide-text(){
+  text-indent: -9999px;
+  overflow: hidden;
+  display: block;
+}
+
+@mixin vertically-and-horizontally-centered ( $height, $width ) {
+  left: 50%;
+  margin-left: -$width / 2;
+  //margin-top: -$height / 2;
+  min-height: $height;
+  min-width: $width;
+  position: absolute;
+  top: 150px;
+}

lms/static/sass/base/_mixins.scss

@@ -1,24 +0,0 @@
-@function em($pxval, $base: 16) {
-  @return #{$pxval / $base}em;
-}
-
-// Line-height
-@function lh($amount: 1) {
-  @return $body-line-height * $amount;
-}
-
-@mixin hide-text(){
-  text-indent: -9999px;
-  overflow: hidden;
-  display: block;
-}
-
-@mixin vertically-and-horizontally-centered ( $height, $width ) {
-  left: 50%;
-  margin-left: -$width / 2;
-  //margin-top: -$height / 2;
-  min-height: $height;
-  min-width: $width;
-  position: absolute;
-  top: 150px;
-}

lms/static/sass/base/_mixins.scss

@@ -0,0 +1 @@
+../../../../common/static/sass/_mixins.scss