make sure compound PCA biplot has the right aspect ratio

as requested in #49


Former-commit-id: 1c3938a081be5b900b7199fdca1f014182f78504

ippisite/ippidb/templates/base.html

@@ -130,6 +130,7 @@
                     type: 'scatter',
                     data: scatterData,
                     options: {
+                        maintainAspectRatio: true,
                         scales: {
                             xAxes: [{
                                 type: 'linear',

ippisite/ippidb/templates/compound_card.html

@@ -162,7 +162,7 @@
               <h5 class="card-header">PCA : iPPI-DB chemical space</h5>
               <div class="card-body">
 
-              <canvas id="pca_biplot"></canvas>
+              <canvas id="pca_biplot" style="width:600px; height:600px;"></canvas>
               <script>
                 drawCompoundsBiplotChart('pca_biplot', {{ compound.id }}, '{{ compound.best_pXC50_activity_ppi_family|default_if_none:"No target family identified" }}', {{ pca_biplot_data | safe }}, 'physicochemistry');
               </script>