increase indentation to make ghc 7.8 parser happy
tweak for ghc 7.8: DeriveTraversable and base <4.8
only call forestFromMeta once per new meta

previously it was once per signal treestore
derive Functor/Applicative for some Monads
allow ctrl-c to interrupt ipopt without killing it

Now an IPOPT callback is always created, and if ctrl-c is detected the callback will return False, telling IPOPT to gracefully terminate evaluations
don't rebuild signal tree if n and deg are changed, only if names are chnaged
add rocket example