Tweak server schema for Normalised Summaries

- Change InfrastructureType to Infrastructure as this complies with the
  message format.
- Update some Normalised fields to be BIGINT UNSIGNED as they will be
  large positive numbers.
Tweak ApelMysqlDb for normalised summaries

- Change MYSQL_TABLES to use view for NormalisedSummaries, rather than
  parent table, in the same way that Summaries does.
Add support for normalised summaries to unloader

- Add headers and record types for normalised summaries.
- Change unload_latest_super_summaries to work on normalised super
  summaries instead.