HC-1025 [Into Hydra Branch] restore image.bytes

Into main hydra branch (not new pdfjs code).

Copied from pre-subtree hydra:
https://github.com/bovardtiberi-wf/pdf_client_service/pull/30
--------------

We do not want to erase image.bytes as there may be other references to this same image object in other parts of the pdf.

Test with the Box/pdf*/*Crow_demo_092512.pdf. Page 11 uses about five references of the small spreadsheet screenshot image: http://screencast.com/t/Io4eW697se52

@bovardtiberi-wf 
@jonmccracken-wf 
@ryanjackson-wf