Added documentation on function configuration behavior
In Rafter, some functions take configuration arguments, such as 'debug', and thus they are configurable functions.

All configurable functions must have default values for their configuration options in their home modules' specification, more precicely in the 'conf' object in the JSON-file carrying that specification.

Functions can inherit configuration argument values from their caller. As both the caller and the callee has configuration values, one must precede over the other.

For the 'debug' configuration parameter, the following behavior apply:

Caller function      | Callee function
debug argument given | default debug argument
---------------------+--------+---------
                     |  TRUE  |  FALSE
---------------------+--------+---------
TRUE                 |  TRUE  |  TRUE
FALSE                |  TRUE  |  FALSE
NOT GIVEN            |  TRUE  |  FALSE

Thus it can be seen that TRUE tricles down through function calls while FALSE does not tricle down. Thus the only way to except a function from a preceding TRUE value given by the caller, is to strip away the debug lines in the preceded callee function. Tough luck.