ERP5 Historical Comparison View

This MR uses DiffTool to show the diff between Historical revisions of any ERP5 objects in both XHTML and renderJS UI. In the Diff Tool, we use deepdiff python library to calculate diff between 2 versions of any object and then display the diff.

renderJS UI view: XHTML UI view

Before the same view used to be with old_value, new_value and current_value

NOTE: This MR is predecessor to the full work on DiffTool here : https://lab.nexedi.com/nexedi/erp5/merge_requests/686

This MR requires the slapos change : https://lab.nexedi.com/nexedi/slapos/merge_requests/343