Multi user features :

->Use Usr App related fonctions instead of Global App related Functions
->Manage properly icon path for each user

BUG=XWALK-2249

Change-Id: I5be59d0264aed84f708273b58061c8834dd63404
Signed-off-by: Sabera Djelti (sdi2) <sabera.djelti@open.eurogiciel.org>
Signed-off-by: Baptiste DURAND <baptiste.durand@open.eurogiciel.org>
Merge pull request #2298 from eurogiciel-oss/multiuser_xwalk_2249

Multi user features :