Feature Add: Optional reject of 'Cell' based GPS data

Added:

• You can now set in the .ini configuration file to ignore any GPS data that comes from cellular triangulation and only accept the more precise data that comes from Wifi, GPS or GPS-Course.
• This feature is turned OFF by default.
• All configuration items for this feature have been added to the end of the .ini.sample file.

Fixed:

• Changed logging level for GPS data validation checks that are configured to be ignored from a warning to a simple debug message.