scripts: added script to split raw iq dump files

gr_grc/scripts/split_file.py

+#!/usr/bin/env python2
+# -*- coding: utf-8 -*-
+
+import sys
+import numpy as np
+
+file = sys.argv[1]
+start = int(sys.argv[2])
+end = int(sys.argv[3])
+
+data = np.memmap(open(file), mode="r", dtype=np.complex64)
+split_data = data[start:end]
+
+split_data.tofile(open("filename2", "r+"))
+