Added new tool: snmpwalk-worker

Small tool that queries SNMP devices. It produces the output
that is used by snmp/snmp_preprocess.py
Added two more tools

- dump_data_dir.py
	Uses the output of the snmpwalk-worker to generate
	temporary files that can be used to update rrd files
- update-rras
	Usese the output of dump_data_dir to update a list
	of rrd files
Begin time calculation if all files are known.
Added some comments.
Make sure that the tag _id is changed on the fly
snmp_preprocess: IP range calculation optimization

The ip ranges for cEigrp and ipCidrRoute have perviously
been calculated using database requests after the parsing
was completed. We are now creating them on the fly while
inserting the data into the DB:
SQL backends: allow insert instead of update
Merge branch 'master' into merge-from-timm