Use a (mostly) hermetic Python interpreter

It still requires python to be installed on the host to run the wrapper
scripts, but it's close to being fully hermetic.

This also requires/enables the following changes, unfortunately all at
the same time:
 * Use a downloaded f2py
 * Use a downloaded scipy/numpy/matplotlib
 * Fix a few things that don't run with the python version in their #!
 * Stop using bazel-generated __init__.py files, because those interfere
   with importing matplotlib nicely

Change-Id: Ife280464613d67cece9587b7d947f0b1d5466d7e
diff --git a/debian/patchelf.BUILD b/debian/patchelf.BUILD
new file mode 100644
index 0000000..423de57
--- /dev/null
+++ b/debian/patchelf.BUILD
@@ -0,0 +1,5 @@
+filegroup(
+    name = "patchelf",
+    srcs = ["usr/bin/patchelf"],
+    visibility = ["//visibility:public"],
+)