introduce database patch level for version

This will be needed later for automatic migrations.

nominatim/tools/exec_utils.py

@@ -134,7 +134,7 @@ def run_osm2pgsql(options):
 def get_url(url):
     """ Get the contents from the given URL and return it as a UTF-8 string.
     """
-    headers = {"User-Agent" : "Nominatim/" + NOMINATIM_VERSION}
+    headers = {"User-Agent" : "Nominatim/{0[0]}.{0[1]}.{0[2]}-{0[3]}".format(NOMINATIM_VERSION)}
 
     try:
         with urlrequest.urlopen(urlrequest.Request(url, headers=headers)) as response: