[dbg] Pull out common code into dbg-lib

- Modularize common routines
- Extract the block_dumper interface for displaying blocks
- Remove inheritance from show_traits

dbg-lib/commands.h

@@ -0,0 +1,24 @@
+#ifndef DBG_COMMANDS_H
+#define DBG_COMMANDS_H
+
+#include "dbg-lib/command_interpreter.h"
+#include "dbg-lib/block_dumper.h"
+#include "persistent-data/block.h"
+
+//----------------------------------------------------------------
+
+namespace dbg {
+	dbg::command::ptr
+	create_hello_handler();
+
+	dbg::command::ptr
+	create_exit_handler(dbg::command_interpreter::ptr interp);
+
+	dbg::command::ptr
+	create_block_handler(persistent_data::block_manager::ptr bm,
+			     dbg::block_dumper::ptr dumper);
+}
+
+//----------------------------------------------------------------
+
+#endif