adding leave tangle end-point
update preview_request API
Merge pull request #232 from ndomar/C3_sak93_S131_modifypreviewRequestAPI

API_S[131]_UpdateAPI
Merge pull request #237 from ndomar/C1#HebaAamer#19_API_adding_leave_tangle_endpoint

API_S[19]_AddLeaveTangleEndPoint
Issue #174 - Fix API conflicts