Add Mongodb Operator

[sharego]

Add a basic Mongodb operator, which work fine on: kubernetes version:

Client Version: v1.16.2
Server Version: v1.15.5

kudo version:

KUDO Version: version.Info{GitVersion:"0.8.0", GitCommit:"06c92b76", BuildDate:"2019-11-30T07:10:53Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}

[kensipe]

sorry for delay... I will look at this today

[zmalik]

thank you @sharego can you please add the operator here https://github.com/kudobuilder/operators/blob/master/kudo-test.yaml#L15 ? so the CI can test the operatorversion installation at least.