feat(svg_icon): Add standard svg icons

-Adds icons to use with the svg_icon smarty helper in the is_themecore module. See is_themecore-PS9 repo.

- Uses chevron svg icons by default on bootstrap touchspin AND on main menu if it has children.

falcon/modules/ps_mainmenu/ps_mainmenu.tpl

@@ -20,6 +20,11 @@
               {if $node.open_in_new_window} target="_blank" {/if}
             >
               <span class="align-self-center">{$node.label}</span>
+              {if $node.children|count}
+                <span class="d-none d-md-block pl-1" style="margin-bottom: 3px;">
+                    {svg_icon file='chevron_down.svg' }  
+                </span>
+              {/if}
             </a>
             {if $node.children|count}
             {* Cannot use page identifier as we can have the same page several times *}
@@ -51,4 +56,4 @@
   <div class="main-menu" id="_desktop_top_menu">
     {menu nodes=$menu.children}
   </div>
-</div>
+</div>