Fixed the shebang lines on the Python scripts.

Also, removed the one from modules/python/src2/cv.py and cleared its
executable bit, since it's not a script.

modules/java/generator/gen_java.py

@@ -1,4 +1,4 @@
-#/usr/bin/env python
+#!/usr/bin/env python
 
 import sys, re, os.path
 from string import Template

modules/java/generator/gen_javadoc.py

@@ -1,4 +1,4 @@
-#/usr/bin/env python
+#!/usr/bin/env python
 
 import os, sys, re, string, glob
 from optparse import OptionParser

modules/java/generator/rst_parser.py

@@ -1,4 +1,4 @@
-#/usr/bin/env python
+#!/usr/bin/env python
 
 import os, sys, re, string, fnmatch
 allmodules = ["core", "flann", "imgproc", "ml", "highgui", "video", "features2d", "calib3d", "objdetect", "legacy", "contrib", "gpu", "androidcamera", "java", "python", "stitching", "ts", "photo", "nonfree", "videostab", "ocl", "superres"]