Duniter universal dividend pallet

One of the main features of Duniter is the Universal Dividend based on the Relative Theory of Money. It is both a daily monetary creation and a measure unit.

This pallet provides functions to create UDs and transfer an amount of currency counted in UD. It should be noted that the UD is not actually created every day on every account which would be very resource consuming but must be claimed by the member in a given extrinsic.