Change some types to string unions, make m.redraw.strategy a BasicProperty<T>
Change some types to string unions, make m.redraw.strategy a BasicProperty<T>

In the latter case, the type already structurally satisfied that type.
Changing m.redraw.strategy simplifies the definition file, and aligns with
the docs.

lhorie/mithril.js,tivac/mithril.js,tivac/mithril.js,impinball/mithril.js,pygy/mithril.js,MithrilJS/mithril.js,lhorie/mithril.js,impinball/mithril.js,barneycarroll/mithril.js,barneycarroll/mithril.js,MithrilJS/mithril.js,pygy/mithril.js