Let wallet recovery use 64 byte hex strings and 24 word seeds.

1. Allow wallet recovery from 64 byte hex strings.
2. Allow use of 24 word legacy seeds created from 64 byte hex strings.

lib/bitcoin.py

@@ -163,11 +163,11 @@ def is_old_seed(seed):
 
     try:
         seed.decode('hex')
-        is_hex = (len(seed) == 32)
+        is_hex = (len(seed) == 32 or len(seed) == 64)
     except Exception:
         is_hex = False
 
-    return is_hex or (uses_electrum_words and len(words) == 12)
+    return is_hex or (uses_electrum_words and (len(words) == 12 or len(words) == 24))
 
 
 # pywallet openssl private key implementation