UI: Allow vertical resizing, and use tk.E on Sizegrip

* Without vertical resizing being allowed changing themes can result in
  either some of the bottom of the main frame being hidden, or there being
  extraneous extra space there.  NB: This still does **NOT** allow manually
  resizing vertically, that's a function of how the widgets are set up.

* Sizegrip needs to `sticky=tk.E` not `tk.SE`, as the latter creates extra
  vertical padding that we don't want.

EDMarketConnector.py

@@ -616,9 +616,11 @@ def open_window(systray: 'SysTrayIcon') -> None:
         self.status.grid(row=0, column=0, sticky=tk.W)
 
         # Make the window resizable
-        master.resizable(True, False)
+        # Yes, we need to allow vertical resizing, else theme changing can
+        # cause the botttom of the UI to be irretrievably hidden.
+        master.resizable(True, True)
         ttk_grip = ttk.Sizegrip(self.status_row, name='size_grip')
-        ttk_grip.grid(row=0, column=1, sticky=tk.SE)
+        ttk_grip.grid(row=0, column=1, sticky=tk.E)
         #######################################################################
 
         # Bottom 'status' line.