Rework database to include process info

[EricRahm]

We need to include a process name when adding values to the database and update the the json generation to handle the presence of a process name.

One option is to just shove it in as an additional :metedata field. Preferably we'd add a process name column / table to the DB instead. This might be a good time to split out other metadata fields and add the heap kind from #39 in.

[Nephyrin]

The only thing to be careful of here is old databases -- if we ever want to graph a new line from the existing data, we can add it to create_graph_json.py and nuke the old json, which doesn't work if the database format changes.

I'd been working around this by keeping util/update_database.py aware of all old formats and able to do any -> newest conversion, so if we ever want to re-export an old database, we can just run update on it after unarchive.

[EricRahm]

This is being worked on in #80, I went with the updating the DB schema.

[EricRahm]

Landed on the e10s branch in ae88a34