fix(assets): New toolbar icons, shadows to achieve less heavy edges on messages

Summary: Just visual changes

Test Plan: Run tests

Reviewers: evan

Reviewed By: evan

Differential Revision: https://phab.nylas.com/D1695

internal_packages/message-list/stylesheets/message-list.less

@@ -133,8 +133,8 @@
     padding: 0 0 5px 0;
 
     background: @background-primary;
-    border: 1px solid @border-secondary-bg;
+    border: 0;
-    box-shadow: 0 1px 1.5px rgba(0,0,0,0.14);
+    box-shadow: 0 0px 0.5px rgba(0, 0, 0, 0.28), 0 1px 1.5px rgba(0, 0, 0, 0.08);
     border-radius: 4px;
 
     &:first-child { padding-top: 0; }
@@ -245,7 +245,7 @@
       border-right: 1px solid @border-color-divider;
       border-left: 1px solid @border-color-divider;
       background-color: darken(@background-primary, 2%);
-      box-shadow: 0 1px 1px rgba(0,0,0,0.1)
+      box-shadow: 0 1px 1px rgba(0,0,0,0.1);
     }
   }
 
@@ -355,8 +355,8 @@
     position: relative;
     z-index: 2;
 
-    border: 1px solid @border-secondary-bg;
+    border: 0;
-    box-shadow: 0 1px 1.5px rgba(0,0,0,0.14);
+    box-shadow: 0 0px 0.5px rgba(0, 0, 0, 0.28), 0 1px 1.5px rgba(0, 0, 0, 0.08);
     border-top: 1px dashed @border-color-divider;
     border-radius: 0 0 4px 4px;
     background: @background-primary;

internal_packages/mode-switch/lib/mode-toggle.cjsx

@@ -20,8 +20,8 @@ class ModeToggle extends React.Component
   render: =>
     return <div></div> unless @state.visible
 
-    <div className="mode-toggle mode-#{@state.mode}"
+    <div className="btn btn-toolbar mode-toggle mode-#{@state.mode}"
-         style={order:51, marginTop:10, marginRight:14}
+         style={order:51}
          onClick={@_onToggleMode}>
       <RetinaImg
         name="toolbar-icon-toggle-pane.png"

internal_packages/mode-switch/stylesheets/mode-switch.less

@@ -3,6 +3,7 @@
 .mode-toggle {
     z-index: 1000;
     position: relative;
+    padding-top:5px;
     .content-mask {
       background-color: @text-color-subtle;
     }