Add ability to read arbitrary objects.
Add pdf.File.Info() to return a copy of the document's info dictionary.
Make File.SetCatalog() and File.SetInfo() take *Dictionary arguments rather than *Indirect.
Add Clone() method to Object interface and implementations to all types that implement Object.
Handle setting Info and setting Root in trailer in same way with common code.
Also, add File.Trailer() method to pdf.File to return Clone() of trailer.
Remove unused method Page.BindToFile().
Refactor to provide better support for opening existing files.
Refactor to provide better support for opening existing files.
Merge branch 'read-existing-document' of github.com:mawicks/PDFiG into read-existing-document

Conflicts:
	pdf/indirect.go
Have Indirect.Finalize() return the indirect object.
Use this to simplify some of the Finalize() calls.
Continue refactoring to improve support for reading existing files.
Rename Indirect.Finalize() to Write(); rename Page.Finalize() to Close().