[IOT-1790]Changes in C++ APIs design to remove raw pointers

[IOT-1790]Changes in C++ APIs design to remove raw pointers

1. Callbacks are discovery and subscribtion is updated to smart pointers
2. Message and sync Callbacks are sent as object in place of pointers
3. Create Message and SendMessage are sent and received as objects in place of pointers.

patch 2 : added review comment changes
patch 3 : rebased
patch 4 : added separate files for accepted provider/consumer

Change-Id: I63f2655d51f46851dcc2e2a93fe2adadcff32134
Signed-off-by: Abitha Shankar <abitha.s@samsung.com>
Signed-off-by: abitha.s <abitha.s@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/16961
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
Tested-by: Uze Choi <uzchoi@samsung.com>