Updating UI to cover RHS and the centre channel separately

web/react/components/post_list.jsx

@@ -464,7 +464,7 @@ module.exports = React.createClass({
 
         return (
             <div>
-                <div className='center-file-overlay invisible'>
+                <div className='file-overlay center-file-overlay invisible'>
                     <div>
                         <i className="fa fa-upload"></i>
                         <span>Drop a file to upload it.</span>

web/react/components/post_right.jsx

@@ -296,7 +296,7 @@ module.exports = React.createClass({
 
         return (
             <div className="post-right__container">
-                <div className='center-file-overlay right-file-overlay invisible'>
+                <div className='file-overlay right-file-overlay invisible'>
                     <div>
                         <i className="fa fa-upload"></i>
                         <span>Drop a file to upload it.</span>

web/sass-files/sass/partials/_base.scss

@@ -24,6 +24,7 @@ body {
     height: 100%;
     > .row.main {
       height: 100%;
+      position: relative;
     }
   }
   > .container-fluid {

web/sass-files/sass/partials/_post.scss

@@ -106,13 +106,13 @@ body.ios {
 	}
 }
 
-.center-file-overlay {
-	position: fixed;
+.file-overlay {
+	position: absolute;
 	top: 0;
 	left: 0;
 	width: 100%;
 	height: 100%;
-	background-color: rgba(0, 0, 0, 0.8);
+	background-color: rgba(0, 0, 0, 0.6);
 	text-align: center;
 	color: #FFF;
 	display: table;