cmd/ethereum: improve command line interface

The ethereum command line interface is now structured using subcommands.
These separate the different tasks it can perform.

Almost all flag names are backwards compatible.

The key tasks have not been ported to subcommands since they will be
replaced by the new accounts infrastructure very soon.

Godeps/_workspace/src/github.com/codegangsta/cli/cli.go

@@ -0,0 +1,19 @@
+// Package cli provides a minimal framework for creating and organizing command line
+// Go applications. cli is designed to be easy to understand and write, the most simple
+// cli application can be written as follows:
+//   func main() {
+//     cli.NewApp().Run(os.Args)
+//   }
+//
+// Of course this application does not do much, so let's make this an actual application:
+//   func main() {
+//     app := cli.NewApp()
+//     app.Name = "greet"
+//     app.Usage = "say a greeting"
+//     app.Action = func(c *cli.Context) {
+//       println("Greetings")
+//     }
+//
+//     app.Run(os.Args)
+//   }
+package cli