Validate list of deltas at update notification file.

Validate list of deltas at update notification file.

+Assure that the list of deltas is ordered to facilitate the validation of contiguous serials, and the processing of only the required deltas (only if there's a delta update).
+Change enum 'rrdp_uri_cmp_result' to a type 'rrdp_uri_cmp_result_t'.
+Process the snapshot if there's an error processing deltas.
+Make 'delta_head' attributes public, global and doc data init methods are now void.
+Remove 'SLIST' usage at 'deltas_head' struct, use instead an array list implementation, ready to store a defined amount of elements.