Fix bug in latitude/longitude conversion

Fixed unit test for python3.  int('+ 1') works in python2 but not python3.
Also corrected a unit test.

gramps/gen/utils/place.py

@@ -116,9 +116,12 @@ def __convert_using_colon_repr(stringValue):
     # if no characters before ':' nothing useful is input!
     if len(l[0]) == 0:
         return None
-    if l[0][0] == '-':
-        sign = '-'
-        l[0]=l[0][1:]
+    if l[0][0] in ['+', '-']:
+        sign = l[0][0]
+        l[0]=l[0][1:].strip()
+        # regard a second sign as an error
+        if l[0][0] in ['+', '-']:
+            return None
     else:
         sign = '+'
     try:

gramps/gen/utils/test/place_test.py

@@ -202,7 +202,7 @@ class PlaceTest(unittest.TestCase):
         self._test_formats_fail(lat, lon)
 
         lat, lon =  '-50:10:1', '-+2:1:2'
-        self._test_formats_success(lat, lon)
+        self._test_formats_fail(lat, lon)
 
     def test_missing_minute(self):
         lat, lon =  '-50::1', '-2:1:2'