Standardize errors in csp-config

[smarlowucf]

Currently the errors list in csp-config is expected to be a list of strings. However, some error strings contain a mix of text and marshalled json. This format is not ingestible in a way that it could be easily parsed.

Errors should be either a marshalled json string with a standard set of keys such as title, description. Or they should all be flat strings with no structured data.

[smarlowucf]

Also, consider including a timestamp somehow which could be used to pinpoint the location in the log file where the error occurred. This could be useful for debugging the problem.

[rtamalin]

Marshalled JSON would make it easier for machine processing, and still be reasonably human readable.

Even if we don't use marshalled JSON it should still be possible to "structure" the content of a error message string, e.g. the string construction process can include a prefix that is the time the issue occurs at, and some other useful info...

Potentially we could handle/implement this in the base CSPBillingAdapterException, so that the str() renders the desired structured string format, and add a json() method that can produce the marshalled JSON format...

[smarlowucf]

The offending error messages have been cleaned up. There should be no more embedded json in error messages. However, we can leave this open to still consider more robust error messaging. This is also tangential to #89 .