Bug 20996: Remove prefix use of borrower category

Bug 20996: Remove prefix use of borrower category

This patch removes the potential use of borrower category as a ILL
request ID prefix. It makes no sense. We provide the ability for a site
to define a request prefix based on branch, there is no use case for
using the borrower category. Add to this that the borrower for every
request was being retrieved in order to get the category, it's a huge
performance hit also.

We also now require the <branch> block in the <interlibrary_loans> block
and complain if it's not present. The request prefix should be defined
in this block.

This patch also improves the performance of the API request that returns all
requests, optionally including additional data.

It also deprecates the overloaded TO_JSON method and moves the request
augmentation code into the API route's controller. It may be that we
want to shift it out of there at some point, but it is fine where it is
for now.

Signed-off-by: Magnus Enger <magnus@libriotech.no>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>