Merge tag 'v1.5.0rc2' into develop

Synapse 1.5.0rc2 (2019-10-28)
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Bugfixes
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- Update list of boolean columns in `synapse_port_db`. ([\#6247](https://github.com/matrix-org/synapse/issues/6247))
- Fix /keys/query API on workers. ([\#6256](https://github.com/matrix-org/synapse/issues/6256))
- Improve signature checking on some federation APIs. ([\#6262](https://github.com/matrix-org/synapse/issues/6262))

Internal Changes
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- Move schema delta files to the correct data store. ([\#6248](https://github.com/matrix-org/synapse/issues/6248))
- Small performance improvement by removing repeated config lookups in room stats calculation. ([\#6255](https://github.com/matrix-org/synapse/issues/6255))