Fix local includes

With Enginio/ the build directory version of the file
will be picked up first.
Merge pull request #117 from gladhorn/includes

Fix local includes
Fix EnginioModel::operation property type.
Merge pull request #120 from nierob/setOperation

Fix EnginioModel::operation property type.
Merge pull request #122 from nierob/smallFixups

Remove buggy and unused forward declarations
Fix potential memory leak in EnginioModel