Raise ConfigException when using incorrect Column syntax

The syntax for the columns parameter is restricted,
only supporing Lxy, Dxy and Pxy (and qualifiers).

Using incorrect syntax resulted in an uncaught, scary exception [1].

Let's properly raise an exception in ColumnConfigMaker,
catch it in parse_config_properties and re-raise as ConfigException.

Bug: T284183

[1] <class 'AttributeError'> 'NoneType' object has no attribute 'get_key'