Add a debugging mode to update-bcd

[queengooborg]

This is something we should implement as a part of #571.

Sometimes, when I view results from the collector and perform more research, I wonder how the collector had come to such a conclusion. It would be great to include a command line flag (like -d) that tells the update script to add __collector_reason keys to BCD, or perhaps a logfile, which includes the data used in setting the version number.