Implement packages and versions reporting in the metrics database

[Evan]

Sticking this on Daisy for lack of a better place to put it.

Context from IRC:
[16:42:53] <stgraber> heya
[16:43:01] <ev> hi
[16:43:31] <stgraber> was talking with Steve earlier about the crash database. I was mostly wondering whether we get a full package list + versions into the crash database every time the user submits a crash
[16:43:45] <ev> not at present
[16:43:51] <ev> that's a goal of the metrics database though
[16:44:11] <stgraber> ok. Would be a pretty cool addition as we could then know for a fact that a package in -proposed didn't regress
[16:44:32] <ev> I'm not sure I follow
[16:44:58] <ev> every time we get a crash we get the version of the package that crashes and the versions of all its dependencies. We do not yet get the versions of every package on the system
[16:45:33] <stgraber> yes, but the problem at the moment is that we don't know if something is fixed or if it's just that nobody uses it
[16:45:53] <ev> ahhhhhhh
[16:45:56] <ev> I see what you're saying
[16:45:58] <ev> right
[16:46:02] <stgraber> having a dump of all packages and versions every time, would let us know that we have X people who reported other crashes that have our new package from -proposed and didn't report a crash against it
[16:47:02] <stgraber> currently Steve assumes that we have at least 2000 people running proposed as that's the number of crashes we got last time we badly regressed in -proposed, but it'd be nice to have a more reliable metric that doesn't depend on us pushing broken packages to get the number ;)