Add an entry to a table containing a single column. Checks existing
    table entries to avoid duplicate entries if the given value already
    exists in the table.

    Parameters
    ----------
      tableName : string
        Name of table to add entry to.

      columnHeading : string
        Name of column heading.

      newValue : string
        New value to add to table.

def _AddToSingleColumnTable(self, tableName, columnHeading, newValue):
    """
    Add an entry to a table containing a single column. Checks existing
    table entries to avoid duplicate entries if the given value already
    exists in the table.

    Parameters
    ----------
      tableName : string
        Name of table to add entry to.

      columnHeading : string
        Name of column heading.

      newValue : string
        New value to add to table.
    """
    match = None
    currentTable = self._GetFromSingleColumnTable(tableName)

    if currentTable is not None:
      for currentValue in currentTable:
        if currentValue == newValue:
          match = True

    if match is None:
      goodlogging.Log.Info("DB", "Adding {0} to {1} table".format(newValue, tableName), verbosity=self.logVerbosity)
      self._ActionDatabase("INSERT INTO {0} VALUES (?)".format(tableName), (newValue, ))
    else:
      goodlogging.Log.Info("DB", "{0} already exists in {1} table".format(newValue, tableName), verbosity=self.logVerbosity)

  ############################################################################
  # _GetFromSingleColumnTable
  ############################################################################
    """
    Get all entries from a table containing a single column.

    Parameters
    ----------
      tableName : string
        Name of table to add entry to.

    Returns
    ----------
      list or None
        If either no table or no rows are found this returns None, otherwise a
        list of all table entries is returned.
    """