Remove empty pages from ebook version

[andrejbauer]

The empty pages which make sure that chapters start on odd pages, etc., don't make sense in the ebook format, and quite possibly also in the online version.

[JasonGross]

I haven't looked at the LaTeX code, but I suspect the solution to this (if it's still open) is to use \cleardoublepage, which brings you to a new page in one-sided mode, and brings you to a new odd page in twoside mode.