Update Khufu's file retrieval system

src/stash/scss/_global.scss

@@ -1,5 +1,5 @@
 @import "global/colors", "global/fonts", "global/measurements",
-  "global/animations";
+  "global/animations", "global/zindex";
 html,
 body {
   margin-left: auto;

src/stash/scss/global/_zindex.scss

@@ -0,0 +1,4 @@
+$stashbarIndex: 200;
+$contextMenuIndex: 300;
+$fudIndex: 100;
+$downloadsIndex: 100;

src/stash/scss/stash/StashContextMenu.scss

@@ -6,7 +6,7 @@
   background: lighten($sectionMenuOptions, 10%);
   box-shadow: 1px 3px 2px lighten ($sectionMenuOptions, 5%);
   color: $foreground;
-  z-index: 300;
+  z-index: $contextMenuIndex;
   width: 100%;
   max-width: inherit;
   font-size: 1rem;

src/stash/scss/stash/StashUploadDialog.scss

@@ -16,7 +16,7 @@ $actionButtonSize: 25px;
   max-height: 250px;
   overflow: hidden;
   -webkit-transform: translate3d(0, 0, 0);
-  z-index: 100;
+  z-index: $fudIndex;
   display: block;
   visibility: hidden;
 }

src/stash/scss/stash/Stashbar.scss

@@ -2,7 +2,7 @@
 
 .stashbar {
   width: 100%;
-  z-index: 200;
+  z-index: $stashbarIndex;
 }
 .stashbar-menu {
   width: 100%;