juwang-creating driver config files for C# clients-REEF-50

Currently, for .Net clients to submit a job through REST API, they have launch Java bridge client to generate driver.config with clr arguments. It requires .NET clients to have java installed at their machine and run java program. This PR is to provide a solution for it so that C# clients only need to write C# code to generate driver.config file. 

It contains the code that generates driver.config, httpServer.config and nameServer.config at java side for bridge driver. 
It serializes class hierarchy for the configurations
It provides default implementation for HttpServer that does nothing for the case if HttpServer is not bound. 
It added interface for NameServer and provided Default NameServerImpl for the case if NameServer is not bound. 

This is to address issue https://issues.apache.org/jira/i#browse/REEF-50?filter=-2


The execution of the config files generation is defined in the pom file so that it is always generated on the fly to reflect the latest changes. The config files and class hierarchy generated are packed in the jar file  after build.