Changes

Proper closing of resources in MessageAction
Added the following methods
* clearFiles(Consumer)
* clearFiles(BiConsumer)
This should allow users to close any of their provided resources, 
additionally clearFiles() will now close any opened FileInputStreams!
I've added a note to the class-level documentation that the execution of
MessageAction closes all provided resources. You cannot send the same
resource twice without copying it first!
closes #660
 (commit: b8e7e4e)