Add support for Archos Safe-T mini hardware wallet (#4445)

commit 10c46477f3a6f2fbc0596345511e0994253081eb
Author: SomberNight <somber.night@protonmail.com>
Date:   Wed Jul 25 19:40:05 2018 +0200

    backport changes of trezor plugin

commit 213619e880f709188c1ea6272758896748e681a8
Merge: a855b75b6 6899ca252
Author: Jean-Christophe Rona <jc@rona.fr>
Date:   Wed Jul 25 18:45:19 2018 +0200

    Merge branch 'master' into safe-t-mini

commit a855b75b6f5af5f707c4680d0bac79eb66a85ace
Author: Jean-Christophe Rona <rona@archos.com>
Date:   Wed Jul 25 18:37:12 2018 +0200

    Safe-T: Switch to safet 0.1.3 to remove the rlp dependency

commit 9bee44ca33289158c91c03d47dec45de6577f17b
Author: SomberNight <somber.night@protonmail.com>
Date:   Wed Jul 18 14:01:10 2018 +0200

    safe-t: bump min fw to 1.0.5

    older fw has a bug when restoring from seed

commit 01816607e8ba308cb5cff96b5fb844e4f6b8fcc1
Author: SomberNight <somber.night@protonmail.com>
Date:   Wed Jul 18 13:57:17 2018 +0200

    safe-t: fix rlp version to avoid eth stuff

commit 430206bea1fa10b762ff953fbc7652ce0d0e939d
Merge: a999ae266 b4b862b0c
Author: SomberNight <somber.night@protonmail.com>
Date:   Wed Jul 18 13:29:41 2018 +0200

    Merge branch 'master' into pr/4445

commit a999ae266f499f180946d53d4e860cc871d562ab
Author: Jean-Christophe Rona <rona@archos.com>
Date:   Tue Jun 19 14:18:03 2018 +0200

    Safe-T mini: Remove supported coins

    This is not really useful there.

commit 7922df1031b2c4b132f7f9c90232480b5bf9585c
Author: Jean-Christophe Rona <rona@archos.com>
Date:   Tue May 29 16:43:37 2018 +0200

    Safe-T mini: Add support for the Safe-T mini

electrum/transaction.py

@@ -672,7 +672,7 @@ class Transaction:
 
         `signatures` is expected to be a list of sigs with signatures[i]
         intended for self._inputs[i].
-        This is used by the Trezor and KeepKey plugins.
+        This is used by the Trezor, KeepKey an Safe-T plugins.
         """
         if self.is_complete():
             return