fix(web(js)): improve validation of email addresses

Overwrite the AngularJS validation and transformation of email inputs in
order to support umlauts and eszett.

UI/WebServerResources/js/Preferences/AccountDialogController.js

@@ -16,6 +16,7 @@
     this.account = account;
     this.accountId = accountId;
     this.hostnameRE = usesSSO && accountId > 0 ? /^(?!(127\.0\.0\.1|localhost(?:\.localdomain)?)$)/ : /./;
+    this.emailRE = String.emailRE;
     this.addressesSearchText = '';
     this.ckConfig = {
       'autoGrow_minHeight': 70,