Added ELECTRUMDIR env variable (#5543)

Simple way for allowing users to change localization of Electrum directory
from ~/.electrum to somewhere else

electrum/util.py

@@ -566,7 +566,9 @@ def xor_bytes(a: bytes, b: bytes) -> bytes:
 
 
 def user_dir():
-    if 'ANDROID_DATA' in os.environ:
+    if "ELECTRUMDIR" in os.environ:
+        return os.environ["ELECTRUMDIR"]
+    elif 'ANDROID_DATA' in os.environ:
         return android_data_dir()
     elif os.name == 'posix':
         return os.path.join(os.environ["HOME"], ".electrum")