- Users table model renamed to UsersTableModel- causes linker conflict

with class TableModel in accomodation plugin.
- Edit record dialog is now screen centered.
- Plugin tabs in application main window are now closable.

application/mainwindow.ui

@@ -31,6 +31,9 @@
       <property name="currentIndex">
        <number>-1</number>
       </property>
+      <property name="tabsClosable">
+       <bool>true</bool>
+      </property>
      </widget>
     </item>
    </layout>
@@ -41,7 +44,7 @@
      <x>0</x>
      <y>0</y>
      <width>825</width>
-     <height>25</height>
+     <height>21</height>
     </rect>
    </property>
    <widget class="QMenu" name="menuFile">