Specify EventData type returned from getPastEvents

At the end of each contract's type definition, 'getPastEvents()' is defined, taking the event name as a string parameter, returning an array of EventData[] which should be more specifically typed to connect the specific type of EventData to the name of the event.

The event interfaces exported near the top of a contract file are also not related to the EventData interface.

#765 is related to an attempt to work around this and can have other benefits, but fixing this directly is also desirable.