[data extractor] Properly initilize point properties on project load.

Description

When loading a project with a DataExtractor, retransform the points after the parent (image or curve) was set and we can determine the properties of the parent (symbol, etc.) that are used to draw the points.

Fixes a crash in the project attached in issue #941 (closed)

Conformity

• Changelog entry
• Unit tests
• Update INSTALL
• Downport
• Fixes: #941 (closed)

When external dependencies are removed

• Reporting to ...