Make manual creation of holdings and items easier by implementing custom holding and item templates

Steps to reproduce:

Go to Inventory, and click New Hodling or New Item, and enter the relevant data in the correct fields.

Expected result:
A holding/item template (that you select from a list of custom, predefined templates) makes sure that you see only the fields relevant to the type of material you are cataloging. Some fields are even prepopulated with data typical for the type of material.

Actual result:
Every cataloguer needs to identify (probably with the help of a manual/instructions) which fields we use for our data, and then find those among all the other fields that they will not be using.