GitLab

* Add BGNN example

* Update bgnn example

* Remove uncessary files

* update model index

* style fix

* Add Readme for BGNN example

* Update documentation; remove preprocessing
Co-authored-by: s.ivanov <s.ivanov@mesos-slave080-am6.central.criteo.prod>
Co-authored-by: s.ivanov <s.ivanov@mesos-slave150-am6.central.criteo.prod>
Co-authored-by: Quan Gan <coin2028@hotmail.com>
Co-authored-by: s.ivanov <s.ivanov@mesos-slave148-am6.central.criteo.prod>
Co-authored-by: s.ivanov <s.ivanov@mesos-slave078-am6.central.criteo.prod>
Co-authored-by: Minjie Wang <wmjlyjemaine@gmail.com>