location-importer.in: keep track of sources for networks, ASNs, and organisations

location-importer.in: keep track of sources for networks, ASNs, and organisations

This allows us to trace back concrete changes or anomalies to their RIR
source, without having to parse everything again. Further, it enables
adding 3rd party sources such as IP feeds from Amazon, without loosing
track of the changes introduced by them.

The second version of this patchset uses ALTER TABLE to add the source
columns, avoiding breaking existing SQL setups.

Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>