Use full_shelfkey in shelfkey XML field instead callnumber object

Example: `/view/351080.request?lib=SAL3`

#### Before
![351080-before](https://cloud.githubusercontent.com/assets/96776/5445990/d24ac82e-846d-11e4-82a3-680f4729d4a3.png)

#### After
![351080-after](https://cloud.githubusercontent.com/assets/96776/5445991/d24c6850-846d-11e4-81d9-91295c4d9082.png)