Bug 21232: Add a client-side check on biblionumber when creating a subscription

Bug 21232: Add a client-side check on biblionumber when creating a subscription

This patch adds an AJAX call to the REST API (/api/v1/biblios/) to
retrieve and display the biblio's title.
On clicking the "next" button a check is done to make sure the title
exists, which means the biblionumber we manually entered is valid (can
we assume a title is mandatory?)

Test plan:
- Create or edit a new subscription
- Enter an invalid biblionumber in the input
=> A friendly note is telling you that the biblio does not exist
- Try to switch to the next screen
=> You get an alert
- Enter a valid biblionumber in the input
=> The title is displayed
=> Try to switch to the next screen
=> It works!

Signed-off-by: hc <hc@interleaf.ie>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>