New API for library configuration

This is the first step into providing (more) configuration options in nDPI.

The idea is to have a simple way to configure (most of) nDPI: only one
function (`ndpi_set_config()`) to set any configuration parameters
(in the present or on in the future) and we try to keep this function
prototype as agnostic as possible.

You can configure the library:
* via API, using `ndpi_set_config()`
* via a configuration file, in a text format

This way, anytime we need to add a new configuration parameter:
* we don't need to add two public functions (a getter and a setter)
* we don't break API/ABI compatibility of the library; even changing
the parameter type (from integer to a list of integer, for example)
doesn't break the compatibility.

The complete list of configuration options is provided in
`doc/configuration_parameters.md`.

As a first example, two configuration knobs are provided:
* the ability to enable/disable the extraction of the sha1 fingerprint of
the TLS certificates.
* the upper limit on the number of packets per flow that will be subject
to inspection

fuzz/fuzz_common_code.c

@@ -57,6 +57,8 @@ void fuzz_init_detection_module(struct ndpi_detection_module_struct **ndpi_info_
     NDPI_BITMASK_SET_ALL(all);
     ndpi_set_protocol_detection_bitmask2(*ndpi_info_mod, &all);
 
+    ndpi_set_config(*ndpi_info_mod, NULL, "filename.config", "config.txt");
+
     ndpi_finalize_initialization(*ndpi_info_mod);
   }
 }