Allow Id of UI App to be empty if all Service Apps type global

Allow Id of UI App to be empty if all Service Apps type global

The wgt service app should have a dummy ui app even if it is not needed
This patch allows the UI app's ID to be empty if all service app types are global

-Before
 <tizen:application id="appid" package="pkgid" required_version="x.x"/> -> Allow
 <tizen:application package="pkgid" required_version="x.x"/> -> Disallow

-After
 <tizen:application id="appid" package="pkgid" required_version="x.x"/> -> Allow
 <tizen:application package="pkgid" required_version="x.x"/> -> Conditionally Allow(If all service app's types global)

Requires:
 [wgt-manifest-handlers]https://review.tizen.org/gerrit/#/c/platform/core/appfw/wgt-manifest-handlers/+/226780/

Change-Id: I2ed942fd7fb16b71a98cdac253bf71ca18cdf067
Signed-off-by: Ilho Kim <ilho159.kim@samsung.com>