SW: replace targetcli + python-urwid with targetcli-fb in GRML_FULL

targetcli exists only in wheezy + experimental nowadays.
Quoting the package description of targetcli-fb:

| The targetcli-fb package is a fork of the "targetcli" code
| written by RisingTide Systems. The "-fb" differentiates between
| the original and this version. Please ensure to use either all
| "fb" versions of the targetcli components -- targetcli, rtslib,
| and configshell, or stick with all non-fb versions, since they
| are no longer strictly compatible.