Rudder

This is a subtask of #2424, and it's aim is to avoid having several identical sections in a multi-valued sectioned PI. It must be fixed on the 2.3 branch.

• When saving a PI in the Scala code of rudder, for each multi-valued section in that PI's PT, check if any two sections contain identical configuration
• Sections containing identical configuration are defined as having all the variables (mandatory and optional) with the same values exactly (case sensitive)
• If any two values of section are identical, silently drop one so that the saved PI has only unique section values
• If an existing PI is saved with no changes compared to the currently saved state, this check should still be performed, to make sure we can easily remove duplicates in existing PI