Multi user features :

->Use Usr App related fonctions instead of Global App related Functions
->Manage properly icon path for each user

BUG=XWALK-2249

Signed-off-by: Sabera Djelti (sdi2) <sabera.djelti@open.eurogiciel.org>
Signed-off-by: Baptiste DURAND <baptiste.durand@open.eurogiciel.org>
For wgt, think it should be "widget.icon.@src", suggest to use ```GetIcon128Key()``` (in application_manifest_constants.h) instead.