Clean-up GlobalDAO (SecureByDefault)

Clean-up GlobalDAO (SecureByDefault)

[Issue#]   LINUXWRT-1028
[Problem]  GlobalDAO has unnecessary API.
[Cause]    N/A
[Solution] Remove "SecureByDefault" API
           - "SecureByDefault" setting uses for WAC(SP-2067).
             As current Tizen WRT haven't consider supporting WAC, remove code regarding "SecureByDefault".
           - SP-2067 The WRT MUST provide a user-configurable 'secure-by-default' preference to enable installation of widgets
                     that are not distributor-signed, with the default value set to "No".
                     If the user selects "Yes",
                     they MUST be shown a warning explaining the potential dangers of installing unsigned widgets.
[Verification] Checking API usage
               - No usage
[SCMRequest] N/A

Change-Id: Ic444ef99d7c09b7d2d5159c7e95b4465dad00012