static void usage()
    {
        System.err.println("\nTo generate code for multiple modules:");
        System.err.println("  java -cp -jar protostuff-compiler.jar modules.properties");

        System.err.println("\nThe properties file would look like:\n");
        System.err.println("modules = foo,bar");
        System.err.println("foo.source = path/to/your/proto/file/or/dir");
        System.err.println("foo.output = java_bean");
        System.err.println("foo.outputDir = src/main/java");
        System.err.println("foo.encoding = UTF-8");
        System.err.println("foo.options = key1:value1,key2:value2");

        System.err.println("bar.source = path/to/your/proto/file/or/dir");
        System.err.println("bar.output = java_bean");
        System.err.println("bar.outputDir = target/generated");
        System.err.println("bar.encoding = UTF-8");
        System.err.println("bar.options = separate_schema,generate_field_map");

        System.err.println("\n===================================================\n");

        System.err.println("\nTo generate code for a single module, execute the jar without args and specify:");
        System.err.println("  -Dsource=path/to/your/proto/file/or/dir");
        System.err.println("  -Doutput=java_bean");
        System.err.println("  -DoutputDir=src/main/java");
        System.err.println("  -Dencoding=UTF-8");
        System.err.println("  -Doptions=key1:value1,key2:value2");
    }
The main execution point of compiling protos.

@author David Yu
@created Jan 5, 2010
protostuff-compiler/src/main/java/io/protostuff/compiler/CompilerMain.java