OTAgent: replace OTCleanup with std::unique_ptr
Merge pull request #83 from toxeus/removeOTCleanup

OTAgent: replace OTCleanup with std::unique_ptr
OTAssetContract: replace OTCleanup with std::unique_ptr
Merge pull request #84 from lclc/otassetcontractcleanup

OTAssetContract: replace OTCleanup with std::unique_ptr
OTItem: replace OTCleanup with std::unique_ptr