Support AutoUpdateMode: Version without pattern

Since 24dd6740 UpdateCheckMode: Tags uses the found tag instead of
regenerating it from the AutoUpdateMode pattern making the pattern
superfluous. This adds support for dropping the pattern and a test case.

fdroidserver/checkupdates.py

@@ -492,7 +492,7 @@ def checkupdates_app(app):
             logging.warning("Can't auto-update app with no CurrentVersionCode: " + app.id)
         elif mode in ('None', 'Static'):
             pass
-        elif mode.startswith('Version '):
+        elif mode.startswith('Version'):
             pattern = mode[8:]
             suffix = ''
             if pattern.startswith('+'):

fdroidserver/metadata.py

@@ -448,7 +448,7 @@ valuetypes = {
                    ["AntiFeatures"]),
 
     FieldValidator("Auto Update Mode",
-                   r"^(Version .+|None)$",
+                   r"^(Version.*|None)$",
                    ["AutoUpdateMode"]),
 
     FieldValidator("Update Check Mode",