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).  Though the information is
scant, 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 actually 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>