In some rare cases it is convenient to store a short array value
as a custom property, e.g. a vector or color. For example, it may
be helpful when importing/exporting certain formats that support
custom or nonstandard attributes on objects.
The custom property storage already can handle arrays in order to
support properties defined via python. The only thing missing is
UI support (and some bugs), and this patch fixes that:
- Allow editing short array properties via Custom Properties panel.
- Fix a UI layout sizing bug triggered by the previous item.
- Fix a dependency graph bug with drivers using such properties.
- Make RNA_*_get_default_array code robust in case of size mismatch.
- Support custom default values for array properties, allowing both an array and a scalar value.