Handle all symbol data, provide query methods

This set of changes reworks the schema a little and adds support for loading all the data contained within Breakpad symbol files. It also adds a query.py with query methods for all the queries that we'll need to do against the data. query.py can be run standalone and it will take as input a logfile that minidump_stackwalk will produce with my instrumentation patch, to replay all the queries that minidump_stackwalk would make for processing a particular dump file.

There are also a few random bug fixes mixed in here.