BIP32_HD_Wallet: Fix address derivation

Unfortunately there was root_name and root_derivation confusion
in the past for classes derived from BIP_32_HD_Wallet.
Address derivation used root_name and so would begin with 'x/'
whereas it should have begun with root_derivation, and so started
with 'm/'.

This fixes that old wart and removes some fudges from the trezor
code that used to work around it.

plugins/trezor/client.py

@@ -98,7 +98,7 @@ def trezor_client_class(protocol_mixin, base_client, proto):
             '''Convert bip32 path to list of uint32 integers with prime flags
             0/-1/1' -> [0, 0x80000001, 0x80000001]'''
             path = []
-            for x in n.split('/'):
+            for x in n.split('/')[1:]:
                 prime = 0
                 if x.endswith("'"):
                     x = x.replace('\'', '')