[FIX] account_asset: moves should use the depreciation line date
[FIX] web: FieldMany2ManyBinaryMultiFiles must extend ReinitializeFieldMixin

The add attachment button should be displayed while being in edit mode, but not in view mode
As the widget depends on the form actual mode, the widget should be re-rendered each time the actual mode changes

This is the point of the ReinitializeFieldMixin class
[MERGE] forward port of branch 7.0 up to d36c8b5