Solution : https://service.sap.com/sap/support/notes/607056 (SAP Service marketplace login required)
Key words : 
customer fields ci_aufk tab index 'line type' enter cnci_aufk, line type development class/package, include    ci_aufk development class/package, customer field ci_aufk add, create data type cnci_aufk, create data type cn_tt_ci_aufk, change user-defined fields, user-defined fields existing, 'components' tab index, development class/package
Related Notes : 
       
| 634869 | SAPKU40001: Support Package 01 for CRM 4.0 | 
| 629115 | Activation error for CNCI_AUFK after Note 607056 | 
| 607000 | Required notes for PS-BAPIs | 
| 570330 | FAQ 2: Customer-specific fields | 
| 522581 | User-defined fields are not displayed | 
| 518124 | CJ20N:Changes are not saved | 
| 420071 | Network costing: Complete costing instead of update | 
| 410768 | Unclear message CN356 during capacity check | 
| 203031 | Order: Change process type not set for change |