Remove safe_eval

We convert all the fields that were storing python code into PYSON.
We add a pyson attribute on field tag to store PYSON value.

issue4416
review6971002

product.py

@@ -109,3 +109,10 @@ class Template:
     @staticmethod
     def default_weight_digits():
         return 2
+
+    @classmethod
+    def view_attributes(cls):
+        return super(Template, cls).view_attributes() + [
+            ('//page[@id="measurements"]', 'states', {
+                    'invisible': Eval('type').in_(NON_MEASURABLE),
+                    })]

view/template_form.xml

@@ -3,8 +3,7 @@
 this repository contains the full copyright notices and license terms. -->
 <data>
     <xpath expr="/form/notebook" position="inside">
-        <page string="Measurements" col="3" id="measurements"
-            states="{'invisible': Eval('type').in_(['service'])}">
+        <page string="Measurements" col="3" id="measurements">
             <label name="length"/>
             <field name="length"/>
             <field name="length_uom"/>