tag: moved code to tag_print.c

Move everything which dumps a tag to a file descriptor to tag_print.c.
This relaxes dependencies and splits the code into smaller parts.

src/command.c

@@ -36,6 +36,7 @@
 #include "dbUtils.h"
 #include "tag.h"
 #include "client.h"
+#include "tag_print.h"
 #include "os_compat.h"
 
 #define COMMAND_PLAY           	"play"