Allow setting an override for createdDate in PdfRendererBuilder

[andy-clapson]

In a similar fashion to this PR: #158, it would be dynamite to be able to specify/override the createdDate in the builder in the saem style as the producer.

My use case is to set some fixed createdDate value - there are cases when I want to generate a PDF with identical inputs and have a hash of the document remain fixed. While having a "true" createdDate value is useful in many cases, there are times (like in automated testing) where it would be useful to be able to hash documents, and be able to rely on there being no volatile, changing tags that might break the hash.