WIP: playground for config.h replacement

This MR is intended for experimenting with ideas in #234 (closed) and not a direct candidate for merge.

bin/add_config_header.py

+import os
+import sys
+
+def add_config_header(config_file, dir):
+  if not os.path.exists(dir):
+    print('directory {} does not exist.'.format(dir))
+    exit(2)
+
+  config_header = '#include <{}>'.format(config_file)
+  for root, dirs, files in os.walk(dir):
+    for filename in filter(lambda f: f.endswith('.hh'), files):
+        file = os.path.join(root,filename)
+        print(file)
+
+        contains_config_header = False
+        with open(file,'r') as f:
+          file_content = [line.rstrip() for line in f.readlines()]
+          for l,line in enumerate(file_content):
+            if config_header in line:
+              contains_config_header = True
+              break
+            if l >= 50:
+              break
+
+        if not contains_config_header and len(file_content) > 0:
+          with open(file,'w') as f:
+            config_header_written = False
+            include_guard_written = 0
+            for line in file_content:
+              # find the include guard
+              if include_guard_written == 0:
+                if line.startswith('#ifndef DUNE_'):
+                  include_guard_written = 1
+                elif line.startswith('#pragma once'):
+                  include_guard_written = 2
+              elif include_guard_written == 1 and line.startswith('#define DUNE_'):
+                 include_guard_written = 2
+              elif include_guard_written == 2 and not config_header_written:
+                f.write(config_header + '\n')
+                config_header_written = True
+
+              f.write(line + '\n')
+
+if __name__ == '__main__':
+  if len(sys.argv) < 3:
+    print('usage: {} <config_file> <dir>'.format(sys.argv[0]))
+    exit(1)
+
+  add_config_header(sys.argv[1], sys.argv[2])