Fixes #12418 - Correct dashboard behaviour for updated gridster

Updated version of gridster changed the widget class from gs_w to gs-w:
ducksboard/gridster.js@c1668d9
This led to a bit of breakage in css and js which is fixed by this commit.
There was also a change in the way the total width of the gridster
element was calculated that required a change to the initialization.

app/assets/javascripts/dashboard.js

@@ -20,7 +20,7 @@ function auto_refresh(){
 function start_gridster(){
     var gridster = $(".gridster>ul").gridster({
         widget_margins: [10, 10],
-        widget_base_dimensions: [82, 340],
+        widget_base_dimensions: [75, 340],
         max_size_x: 12,
         min_cols: 12,
         max_cols: 12,
@@ -37,7 +37,7 @@ function start_gridster(){
 
 function hide_widget(item){
     var gridster = $(".gridster>ul").gridster().data('gridster');
-    var widget = $(item).parents('li.gs_w');
+    var widget = $(item).parents('li.gs-w');
 
     widget.attr('data-hide', 'true').hide();
     gridster.remove_widget(widget);
@@ -46,7 +46,7 @@ function hide_widget(item){
 }
 
 function remove_widget(item){
-    var widget = $(item).parents('li.gs_w');
+    var widget = $(item).parents('li.gs-w');
     var gridster = $(".gridster>ul").gridster().data('gridster');
     if (confirm(__("Are you sure you want to delete this widget from your dashboard?"))){
         $.ajax({

app/assets/stylesheets/gridster.scss

@@ -6,6 +6,7 @@ $row-margin: 10px;
 .gridster ul{
   padding-left: 0;
   list-style: none;
+  max-width: 100%;
 }
 
 $col-margin-left: 15px;
@@ -109,7 +110,7 @@ $col-margin-fallback: 1.5%;
   }
 }
 
-.gs_w {
+.gs-w {
   padding: 19px;
   margin-bottom: 10px;
   border: 1px solid #e3e3e3;

bundler.d/assets.rb

@@ -14,7 +14,7 @@
   #   https://github.com/nubis/gettext_i18n_rails_js/pull/23
   gem 'gettext', '~> 3.1', :require => false
   gem 'multi-select-rails', '~> 0.9'
-  gem 'gridster-rails', '~> 0.1'
+  gem 'gridster-rails', '~> 0.5'
   gem 'jquery_pwstrength_bootstrap', '~> 1.2'
   gem 'jquery-turbolinks', '~> 2.1'
   gem 'select2-rails', '~> 3.5'