Nyall Dawson 208beb7f8c [layouts] Improve logic of splitting layouts into separate layers when
exporting to a multi-layer format

Now, items are either
- placed onto the same layer as other items (simple items like labels, lines, pictures)
- placed onto the same layer as only other items of equal types (semi-complex items like scalebars or pages)
- placed onto their own unique layers (complex items like legends, maps)

Plus lots of tests covering this, where previously there was few
2019-08-12 16:12:03 +10:00
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2019-08-09 08:47:00 +10:00