Introduce module financer-common that hosts common code for server and (web) client

Also various fixes all over the place

financer-web-client/src/main/resources/templates/account/accountDetails.html

@@ -47,7 +47,7 @@
         <td class="hideable-column" th:text="${transaction.id}"/>
         <td th:text="${transaction.fromAccount.key}" />
         <td th:text="${transaction.toAccount.key}" />
-        <td th:text="${transaction.date}" />
+        <td th:text="${#temporals.format(transaction.date)}" />
         <td th:text="${#numbers.formatDecimal(transaction.amount/100D, 1, 'DEFAULT', 2, 'DEFAULT')}"/>
         <td th:text="${transaction.description}" />
         <td th:text="${transaction.recurringTransaction != null}" />