Change the way the state for an electorate is determined

[chrisala]

Currently the state an electorate resides in is determined via intersection with the states layer in the spatial portal.
This often results in multiple states being assigned where the electorate aligns with a state boundary.

Each electorate should be in only one state so we need to either have this as human maintained reference data or make the intersection smarter (e.g. by applying the 5% overlap rule or assigning the state with the greatest percentage overlap)