Ensured Sensor IDs are converted to Strings

Lots of Sensor IDs are numbers but need to be converted to strings for
database operations.  Cleaned up the reading database class to ensure
they are converted to strings.

bmsapp/readingdb/bmsdata.py

@@ -82,6 +82,7 @@ class BMSdata:
         exceptions = ''
         success_count = 0
         for one_ts, one_id, one_val in recs:
+            one_id = str(one_id)   # make sure sensor ID is a string
             try:
                 # Check to see if sensor table exists.  If not, create it.
                 if one_id not in self.sensor_ids:
@@ -113,6 +114,8 @@ class BMSdata:
         The reading is returned as a row dictionary.
         Returns None if no readings are available for the requested sensor.
         """
+        sensor_id = str(sensor_id)   # make sure ID is a string
+
         # address case where sensor id does not exist
         if sensor_id not in self.sensor_ids:
             return None
@@ -127,6 +130,8 @@ class BMSdata:
         'start_tm' and 'end_tm' are UNIX timestamps.  If either are not provided, no limit
         is imposed.  The rows are returned in timestamp order.
         """
+        sensor_id = str(sensor_id)   # make sure ID is a string
+
         # address case where sensor id does not exist
         if sensor_id not in self.sensor_ids:
             return []
@@ -162,6 +167,8 @@ class BMSdata:
         to replacement. If no last reading was present for the sensor, None 
         values are returned.
         """
+        sensor_id = str(sensor_id)   # make sure ID is a string
+
         self.cursor.execute('SELECT * FROM [_last_raw] WHERE id = ?', (sensor_id,))
         rec = self.cursor.fetchone()
         if rec: