Anchor affect bugfix, partially fixes #33

The mirroring part still has design inconsistencies because of rectangles being laid out by their bottom left corner, but as a breaking change, this will be addressed separately, later...

test/outlines/affect_mirror.yaml

@@ -0,0 +1,55 @@
+points:
+  zones:
+    matrix:
+      columns:
+        only:
+      rows:
+        bottom:
+        top:
+  mirror:
+    ref: matrix_only_top
+    distance: 30
+outlines:
+  exports:
+    test:
+      keys:
+        type: keys
+        side: both
+        size: 14
+        bound: false
+      rb:
+        type: rectangle
+        anchor:
+          - ref: mirror_matrix_only_bottom
+            # we do NOT specify `affect: xyr` here
+          - shift: [-3,-3]
+            orient: 30
+        size: [6,6]
+        operation: stack
+      rt:
+        type: rectangle
+        anchor:
+          - ref: mirror_matrix_only_top
+            affect: xyr
+          - shift: [-3,-3]
+            orient: 30
+        size: [6,6]
+        operation: stack
+      lb:
+        type: rectangle
+        anchor:
+          - ref: matrix_only_bottom
+            # again, no `affect: xyr`
+          - shift: [-3,-3]
+            orient: 30
+        size: [6,6]
+        operation: stack
+      lt:
+        type: rectangle
+        anchor:
+          - ref: matrix_only_top
+            affect: xyr
+          - shift: [-3,-3]
+            orient: 30
+        size: [6,6]
+        operation: stack