Add ckDestroy to generated array proxy

[rbuch]

For cases when a user wants to destroy an entire chare array, they broadcast ckDestroy across the array, destroying each element. Instead, it is likely a bit more efficient and semantically a bit cleaner if they destroy the chare array itself directly.

In code terms, this means broadcasting to CkArray::ckDestroy rather than CkArrayElement::ckDestroy. The generated code should be changed so that the generated chare array proxy type has a ckDestroy method that wraps a calls to CkArray::ckDestroy.