More changes to accomodate webview

- Modified configure.ac to use both webkit2 and webkit1 based on gtk version
- Modified Automake file in help/reference/shell/Makefile.am to compile with gtk-doc
- Modified ev-document-model to support epub-documents.
- Modified ev-window for epub documents.
- Modified jobs so epub pages are not rendered.
- Modified ev-document, although I'm not sure if this is necessary.

Still need to figure out where the web view load uri has to be called to actually load pages, from there the puzzle would be much simpler. Hope to get this done in the week, and pick up the pace now that only six weeks of coding remain before final evaluation.