[*_restore] Add progress bar to cache_restore and era_restore.

A lot of refactoring common code between the restore tools.

era/xml_format.h

@@ -1,7 +1,8 @@
 #ifndef ERA_XML_FORMAT_H
 #define ERA_XML_FORMAT_H
 
-#include "emitter.h"
+#include "base/progress_monitor.h"
+#include "era/emitter.h"
 
 #include <iosfwd>
 
@@ -9,7 +10,7 @@
 
 namespace era {
 	emitter::ptr create_xml_emitter(std::ostream &out);
-	void parse_xml(std::istream &in, emitter::ptr e);
+	void parse_xml(std::string const &backup_file, emitter::ptr e, bool quiet);
 }
 
 //----------------------------------------------------------------