fix(conf): don't use cache dir as base for all data dirs

This is a bit tricky but the issue is that in a `for` loop, the loop
variable(s) are shared during the whole iteration. So capturing its
value in the `lambda` as `k=k` doesn't capture the value of the current
iteration, but the value of the last one.
In this code that happened to be `cache`, so all `data_dirs` usage was
ending up with a path under `directory_cache`.

maloja/pkg_global/conf.py

@@ -332,12 +332,14 @@ for identifier,path in data_directories.items():
 			print("Make sure Maloja has write and execute access to this directory.")
 			raise
 
+class DataDirs:
+	def __init__(self, dirs):
+		self.dirs = dirs
 
-data_dir = {
-	k:lambda *x,k=k: pthj(data_directories[k],*x)  for k in data_directories
-}
-
+	def __getitem__(self, key):
+		return lambda *x, k=key: pthj(self.dirs[k], *x)
 
+data_dir = DataDirs(data_directories)
 
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