Add BookJS stuff to the "body" document.
Added Content-Type meta to head.
Merge branch 'devel' into bookjs
Use content type for response based on the request mode.
Separate body HTML creation from body PDF creation.
Initial PDF rendering using BookJS.
Added bookjs/html mode.
BookJS modes are now bookjs/pdf and bookjs/zip
Customized BookJS.
Added module for BookJS specific stuff
Adding the provided CSS to the renderer
Put page size setting in the CSS
Merge branch 'devel' into bookjs
Adding rest of page settings to CSS
Using A5 as the default page size.
OB-56: Fixed parsing of boolean values
Merge branch 'devel' into bookjs

Conflicts:
	lib/objavi/classic/tasks.py
	lib/objavi/fmbook.py
OB-57: adding custom CSS to the bookjs/zip output.
BK-420: Unset environment variables set by Xvfb
OB-42: fixed missing 'alt' attribute for images (epub)