CIRCULATION : the big rewrite...

CIRCULATION : the big rewrite...

This 1st commit reorders deeply the circulation module.
The goal is to :
* have something 100% templated/translatable.
* have something easy to read & modify, to say to customers/users : you can define your circulation rules as you want if you accept to look in C4/Circ/Circ2.pm

The circulation now works :
1=> ask for the borrower barcode (as previously)
2=> ask for the item barcode.
3=> check "canbookbeissued". This new sub returns 2 arrays :
- IMPOSSIBLE : if something is here, then the issue is not possible and is not done.
- TOBECONFIRMED : if something is here, then the issue can be donc if the user confirms it.
4=> if TOBECONFIRMED is set : ask for confirmation, loop. if neither  are set or confirmation flag is set (2nd pass of the loop), then issue.

The IMPOSSIBLE & TOBECONFIRMED hashs contains :
* the reason of the line. always in capitals, with words separated by _ : BARCODE_UNKNOWN, DEBTS ... as key of the hash
* more information, as value of the hash ( TOBECONFIRMED{ALREADY_ISSUED} = "previous_borrower_name", for example)

This commit :
* compiles
* works on certain situations, not on other
* does NOT issue (the line is # )
* does not check issuing rules depending of # of books allowed / already issued

The next step is :
- check issuing rule.
- extend issuing rule to have a 3D array : for each branch / itemtype / borrowertype = issuing number and issuing length.