Add host system metrics.
Write identity key into 'account' object.

This is the beginning of a migration to storing one identity
key per account, instead of the braindead duplication we're
doing now.  Part one of a two-part deployment in the schema
migration process.
Bump version to 0.10
Schema migration for identity keys.
Bumping version to 0.11
Treat account object as authoritative source for identity keys.

Step 3 in migration.
Bumping version to 0.12
Final migration step, remove identity_key column from keys table.
Bump version to 0.13