Continues the work of the material subsystem improvements.
Add support for embedded SVG files. These are not the same
as image files so need to be handled differently.
Add the ability to filter materials in the editor when called from
code. This allows programs to select objects supporting specific
models, complete models, older models, etc.
Updated tests, and refactored code.
New models and materials supporting patterns such as used by the
TechDraw workbench.
fixes#11686 - checks for the presense of a model property before
assinging a value. This can happen when a required model definition is
not available.
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Co-authored-by: Chris Hennes <chennes@pioneerlibrarysystem.org>
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