Add Apecs.Experimental.Reload module for GHCi world persistence

[dpwiz]

Uses foreign-store to persist world state across GHCi reloads, avoiding the need to reinitialize and repopulate worlds during interactive development.

Live on shmup (the world, persisting gloss is its own story...)

ghci> runReloadable initWorld $ collect $ \(Player, Position p) -> Just p
[V2 2.0 2.0]
ghci> :reload
Ok, one module loaded.
ghci> runReloadable initWorld $ collect $ \(Player, Position p) -> Just p
[V2 2.0 2.0]
ghci> runReloadable initWorld $ newEntity (Target, Position 10)
Entity {unEntity = 4}
ghci> :reload
Ok, one module loaded.
ghci> runReloadable initWorld $ collect $ \(e :: Either Player Target, Position p) -> Just (e, p)
[(Right Target,V2 10.0 10.0),(Left Player,V2 2.0 2.0)]