Get a value from an option in a section. Ability to cast to a specific data type; return a default value if the option does not exist, as well as adding the value to the config.
| Parameters : | section :str : 
 option : str 
 default : special, optional 
 add_if_not_existing : bool, optional 
 dtype : special 
 | 
|---|---|
| Returns : | val : special 
 |