Allocate item to user on request + add a request timeout.

[aga11313]

Currently multiple users can request the same item even if there is only one of that item in stock. What I would propose to change it to keep the system fairer to people who request items first would be the following:

• change the request system to allocate the item to the user on request so that it cannot be requested by any other individual.
• to prevent a situation in which a user requests an item and does not come to the hardware desk to claim it we should set a timeout on a request that will then free up that item again to the poll of items

[notexactlyawe]

This is quite a fundamental change and so should be discussed within the team.