0.1.5 First Alpha

First alpha version of 0.1.5

• Fix glyph bounding boxes and paths for Type1 fonts using flexpoints.
• Fix stack overflow when merging some documents.
• Support loading existing documents into PdfDocumentBuilder.
• Performance improvements for multithreaded scenarios.
• Fix checked value for AcroForm checkboxes where the checked state is appearance only.
• New page.GetOptionalContents() partial optional content retrieval support.
• Partial support for colorspace details on IPdfImages.
• Multiple bug-fixes for various font related issues.

Breaking changes:

• PdfDocumentBuilder now implements IDisposable. This disposes the underlying stream by default but this is a MemoryStream normally so not any serious consequences if left undisposed.
• PdfPageBuilder had the AdvancedEditing property removed. The API is now available in the ContentStream methods / properties (this was from #250).