Unknown TOML parameters don’t issue an error

[wtraylor]

Desired behavior: If a parameter is in the TOML file that is not parsed at all, an exception should be thrown, saying that an unknown parameter was encountered.

Reasons:

1. The user might have misspelled an optional parameter and erroneously thinks it is being parsed and used.
2. The user might have misspelled a mandatory parameter and is confronted with the error message that this mandatory parameter couldn’t be found. The user should be notified first that there is a parameter that couldn’t be parsed.