Feature/incremental protobuf

[ljeub-pometry]

What changes were proposed in this pull request?

• Rework of the proto format to allow for appending new updates to an existing file
• Minor improvements to the internal additions apis for edges and node types to simplify the deserialisation implementation
• Adds check for temporal graph properties so they cannot change type
• Fixes a datetime parsing issues in python where naive DateTime was treated as local rather than UTC

Why are the changes needed?

Incremental creation of serialised graphs (especially for the GraphQL server)

Does this PR introduce any user-facing change? If yes is this documented?

No

How was this patch tested?

existing tests and new test to show the incremental serialisation

Issues

This is the first part of #1704

Are there any further changes required?

Actual interface for incremental writing