Added Mitsuba-specific configuraiton files for 'ag' and 'YouCompleteMe'

Ag is an amazing grep replacement which quickly searches the entire codebase for keywords

YouCompleteMe provides code completion in VIM using a Clang backend. The committed configuration file automatically fetches compilation options from config.py.

.agignore

@@ -0,0 +1,5 @@
+dependencies
+build
+data
+Mitsuba.app
+scenes

.ycm_extra_conf.py

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+import os
+import re
+import ast
+
+SCRIPT_PATH = os.path.dirname(os.path.abspath(__file__))
+
+flags = []
+pattern = re.compile('^([A-Z0-9]+)\s*=\s*(\[.*\])')
+with open(os.path.join(SCRIPT_PATH, "config.py")) as f:
+    for line in f:
+        result = pattern.search(line)
+        if result is None:
+            continue
+        key = result.group(1)
+        if 'LINK' in flags or (not 'FLAGS' in key and not 'INCLUDE' in key):
+            continue
+        try:
+            result = ast.literal_eval(result.group(2))
+            if 'INCLUDE' in key:
+                flags += [ '-I' + path.replace('#', '') for path in result ]
+            else:
+                flags += result
+        except:
+            pass
+
+def MakeRelativePathsInFlagsAbsolute(flags, working_directory):
+    if not working_directory:
+        return list(flags)
+    new_flags = []
+    make_next_absolute = False
+    path_flags = ['-isystem', '-I', '-iquote', '--sysroot=']
+    for flag in flags:
+        new_flag = flag
+
+        if make_next_absolute:
+            make_next_absolute = False
+            if not flag.startswith('/'):
+                new_flag = os.path.join(working_directory, flag)
+
+        for path_flag in path_flags:
+            if flag == path_flag:
+                make_next_absolute = True
+                break
+
+            if flag.startswith(path_flag):
+                path = flag[len(path_flag):]
+                new_flag = path_flag + os.path.join(working_directory, path)
+                break
+
+        if new_flag:
+            new_flags.append(new_flag)
+    return new_flags
+
+def FlagsForFile(filename, **kwargs):
+    final_flags = MakeRelativePathsInFlagsAbsolute(flags, SCRIPT_PATH) + ['-x', 'c++']
+    return {
+        'flags': final_flags,
+        'do_cache': True
+    }