We now have a proper PROP_VECTOR_LAYER property in the XCF which will
store the various data relevant to vector layers.
This also fixes saving this new type of layers at all, since it was
broken in MR !773.
- Some coding style bugs.
- Factorize setting vector layer options into
gimp_vector_layer_set_vector_options(), making sure all code paths to
update the options do the same thing.
- Ceil the vector layer size since stroke width is a double. C rounds
towards zero, which means we may still have too small buffer.
This patch improves vector layer UX based on feedback.
In summary:
* Makes vector layer editable from the Path tool
* Adds initial PDB for creating vector layers in scripts
* Size vector layers to the path size, rather than image
* Transform tools utilize the path for resizing
* Path tool automatically selects vector layer path
