feat(mail): Add SOGoMailHideInlineAttachments option to hide attachments when inline. Fixes #5490.

UI/Templates/PreferencesUI/UIxPreferences.wox

@@ -695,6 +695,16 @@
               </md-checkbox>
             </div>
 
+            <div>
+              <md-checkbox
+                  ng-model="app.preferences.defaults.SOGoMailHideInlineAttachments"
+                  ng-true-value="1"
+                  ng-false-value="0"
+                  label:aria-label="Hide inline attachments">
+                <var:string label:value="Hide inline attachments"/>
+              </md-checkbox>
+            </div>
+
             <div>
               <md-checkbox
                   ng-model="app.preferences.defaults.SOGoMailAutoMarkAsReadEnabled"