Bug 22804: OPAC Overdrive JavaScript contains untranslatable strings

Bug 22804: OPAC Overdrive JavaScript contains untranslatable strings

This patch moves untranslatable strings out of overdrive.js and into
opac-bottom.inc where other strings are defined for use in JavaScript
files.

To test you must have OverDrive integration set up, including
OverDriveCirculation. Test the various Overdrive integration features:

 - Placing holds
 - Cancelling holds
 - Checking out
 - Checking in

These features should work as expected.

Signed-off-by: Jesse Maseto <jesse@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>