Set scrollbar colors as global styles (#1484)

* Setting global webkit-scrollbar styles

Signed-off-by: Alex Andreev <alex.andreev.email@gmail.com>

* Removing usage of custom-scrollbar mixin

Signed-off-by: Alex Andreev <alex.andreev.email@gmail.com>

* Set overflow:auto on .Table

Signed-off-by: Alex Andreev <alex.andreev.email@gmail.com>

* Fixing .drawer-content paddings

Signed-off-by: Alex Andreev <alex.andreev.email@gmail.com>

* Cleaning up

Signed-off-by: Alex Andreev <alex.andreev.email@gmail.com>

src/renderer/components/dialog/dialog.scss

@@ -1,7 +1,5 @@
 
 .Dialog {
-  @include custom-scrollbar;
-
   position: fixed;
   overflow: auto;
   left: 0;
@@ -11,6 +9,7 @@
   padding: $unit * 5;
   z-index: $zIndex-dialog;
   overscroll-behavior: none; // prevent swiping with touch-pad on MacOSX
+  overflow: auto;
 
   &.modal {
     background: transparentize(#222, .5);