Tweak the way scopes work

Should make it clearer what a "variable" is and allow more flexibility
in what a variable can be (previously it could only be an object, but
now it can be e.g. a reference to the template or a special shortcut)

blueprintcompiler/language/lambdas.py

@@ -38,9 +38,10 @@ class Lambda(Value, Scope):
         for child in self.children:
             child.emit_xml(xml)
 
-    def get_objects(self):
+    @property
+    def variables(self) -> T.Dict[str, ScopeVariable]:
         return {
-            **self.parent.parent_by_type(Scope).get_objects(),
+            **self.parent.parent_by_type(Scope).variables,
             self.tokens["argument"]: None,
         }