INT-3203 Introduce RemoteFileTemplate

Begin by refactoring `FileTransferringMessageHandler` to use
a `send` operation on RemoteFileTemplate.

Effectively transfer all properties from the adapter to the
template.

This will allow reuse of the send logic from the adapter in
the outbound gateway for `put` and `mput`.

JIRA: https://jira.springsource.org/browse/INT-3203