revert my 2 last commits

        Revert "add System.Net.Http.Formatting to monodroid build"
        Revert "added System.Configuration and System.Security to monodroid build to fix it"

        This reverts commit 85cb9e31763e14f55ab60554a68e8f8b899dd6a3 and
                     commit 6566273367f79b1f928a921cddfe05db4d622e1e.