support generic command-line options

Hadoop commands should all support some common options. For example, it should be possible to specify the namenode, datanode, and, for that matter, any config option, in a generic way.

This could be implemented with code like:

public interface Tool extends Configurable {
void run(String[] args) throws Exception;
}

public class ToolBase implements Tool extends Configured {
public final void main(String[] args) throws Exception

{ Configuration conf = new Configuration(); ... parse config options from args into conf ... this.configure(conf); this.run(); }

}

public MyTool extends ExcecutableBase {
public static void main(String[] args) throws Exception

{ new MyTool().main(args); }

}

The general command line syntax could be:

bin/hadoop [generalOptions] command [commandOptions]

Where generalOptions are things that ToolBase handles, and only the commandOptions are passed to Tool.run(). The most important generalOption would be '-D', which would define name/value pairs that are set in the configuration. This alone would permit folks to set the namenode, datanode, etc.