Add multi-user support

Add multi-user support

Removing user "app" from user list since, in multi-user architecture,
user names aren't known at build time so they can't be used in spec
files.

Removing group "app" from group list since, in multi-user architecture,
the user group is defined by the TZ variable TZ_SYS_USER_GROUP. To use
this variable as a macro in spec file you need to add: "BuildRequires:
libtzplatform-config-devel".

More information about multi-user architecture can be found here:
https://wiki.tizen.org/wiki/Multi-user_Architecture#tizen-platform-
config_usage

Bug-Tizen: PTREL-393
Change-Id: Ice67a8f789176ff195235b1ee7b77e4afa6789f4
Signed-off-by: Kévin THIERRY <kevin.thierry@open.eurogiciel.org>