Add an init/scaffold subcommand

[nicolaferraro]

We can make it easier to start working on a new integration by providing a kamel init or kamel scaffold command.

$ kamel init myroute.groovy
Generates a the file:

myroute.groovy

// camel-k: language=groovy

// you can write your routes here

But it's more interesting with Java:
$ kamel init Integration.java

Integration.java

// camel-k: language=java

import org.apache.camel.builder.RouteBuilder;

public class Integration extends RouteBuilder {
  @Override
  public void configure() throws Exception {
    // you can write your routes here
    
  }
}

[zregvart]

Would be nice if a test template was added also.