purge-db-data.c: new executable to clean nada's database

Inserted new executable to clean up old and unneded data
from NADA's database.
Updated documentation

Updated Changelog and README file
Makefile: Compiling purge-db-data.c

Added puge-db-data to Makefile command
dblayer.c: Added function to clean-up database

Created function to clean-up NADA's database accordingly
to baseline.ini file. All unneeded records are going to
be purged definitively.