kicad: Make reprs more reasonable

This excludes parent back-links from reprs, which would previously blow
up the repr of many objects.

gerbonara/cad/kicad/footprints.py

@@ -405,7 +405,7 @@ class Pad(NetMixin):
     options: OmitDefault(CustomPadOptions) = None
     primitives: OmitDefault(CustomPadPrimitives) = None
     _: SEXP_END = None
-    footprint: object = None
+    footprint: object = field(repr=False, default=None)
 
     def __after_parse__(self, parent=None):
         self.layers = unfuck_layers(self.layers)
@@ -656,7 +656,7 @@ class Footprint:
     models: List(Model) = field(default_factory=list)
     _ : SEXP_END = None
     original_filename: str = None
-    board: object = None
+    board: object = field(repr=False, default=None)
 
     def __after_parse__(self, parent):
         for pad in self.pads:

gerbonara/cad/kicad/schematic.py

@@ -357,7 +357,7 @@ class SymbolInstance:
     # three other uses of the same symbol in this schematic.
     instances: Named(Array(SymbolCrosslinkProject)) = field(default_factory=list)
     _ : SEXP_END = None
-    schematic: object = None
+    schematic: object = field(repr=False, default=None)
 
     def __after_parse__(self, parent):
         self.schematic = parent
@@ -496,7 +496,7 @@ class Subsheet:
     _ : SEXP_END = None
     sheet_name: object = field(default_factory=lambda: DrawnProperty('Sheetname', ''))
     file_name: object = field(default_factory=lambda: DrawnProperty('Sheetfile', ''))
-    schematic: object = None
+    schematic: object = field(repr=False, default=None)
 
     def __after_parse__(self, parent):
         self.sheet_name, self.file_name = self._properties