Switch to new Google Books API; make SSL friendly

Switch to new Google Books API; make SSL friendly

As implied in the title, this commit does two things.  First, it
switches to the new Google Books API (which is both imminent and
also necessary to make SSL calls work).  From what I have read and
experienced, we do not need an API key to do searches and previews.
I have also not hit any kind of unauthenticated limit in several
days of heavy testing, so I would figure we are safe (at this
point) for normal end-user OPAC browsing.

Second, all Google Book requests are now done over https.  This
eliminates the majority of mixed content warnings when browsing
securely, though you still get a warning when you actual do preview
a book.

In addition to possibly implementing protocol detection (rather
than doing https all the time as a "lowest" common denominator),
there are a few minor points where we might consider future changes.
Those points are commented within the code.

Signed-off-by: Dan Wells <dbw2@calvin.edu>
Signed-off-by: Dan Scott <dscott@laurentian.ca>