Minor improvements to PageContentStreamOptimized class

[Nawrok]

Hi,
While using the PageContentStreamOptimized class, which is used in PDStreamUtils, I noticed a couple of drawbacks that can be improved.

• First, it would be good to implement a Closable interface to this wrapper.
• Secondly, you can add constructors in this class analogous to those in the PDPageContentStream class and, as a result, simplify their invocation.
• In addition, you can also provide a method to return the raw stream that is part of this class.

[johnmanko]

@Nawrok I'll run the tests this weekend. If all looks good I'll merge.