Better install wizard

Break out the workflow logic of the install wizard
into a base class.  This means reimplementing with
full support in a new GUI is now easy; you just provide
ways to request passwords, show messages etc.  The API
is fully documented in the base class.

There are a couple of minor outstanding issues, including that
the old messages shown when recovering a wallet are missing.
I will come back to that.  Ledger wallet might be broken.

Other improvements:

The install wizard code is now easy to follow and understand.
Hardware wallets can now be restored without any need for their
accompanying libraries.
Various bits of trustedcoin were broken and have been fixed.
Many plugin hooks can be removed.  I have only started on this.

lib/plugins.py

@@ -26,6 +26,7 @@ import time
 from util import *
 from i18n import _
 from util import profiler, PrintError, DaemonThread
+import wallet
 
 class Plugins(DaemonThread):
 
@@ -38,18 +39,21 @@ class Plugins(DaemonThread):
         else:
             plugins = __import__('electrum_plugins')
         self.pkgpath = os.path.dirname(plugins.__file__)
+        self.config = config
+        self.hw_wallets = {}
         self.plugins = {}
         self.gui_name = gui_name
         self.descriptions = []
         for loader, name, ispkg in pkgutil.iter_modules([self.pkgpath]):
             m = loader.find_module(name).load_module(name)
             d = m.__dict__
-            if gui_name not in d.get('available_for', []):
+            gui_good = gui_name in d.get('available_for', [])
+            details = d.get('registers_wallet_type')
+            if details:
+                self.register_plugin_wallet(name, gui_good, details)
+            if not gui_good:
                 continue
             self.descriptions.append(d)
-            x = d.get('registers_wallet_type')
-            if x:
-                self.register_wallet_type(config, name, x)
             if not d.get('requires_wallet_type') and config.get('use_' + name):
                 self.load_plugin(config, name)
 
@@ -100,15 +104,28 @@ class Plugins(DaemonThread):
                 return False
         return w.wallet_type in d.get('requires_wallet_type', [])
 
-    def wallet_plugin_loader(self, config, name):
-        if self.plugins.get(name) is None:
-            self.load_plugin(config, name)
-        return self.plugins[name]
+    def hardware_wallets(self, action):
+        result = []
+        for name, (gui_good, details) in self.hw_wallets.items():
+            if gui_good:
+                try:
+                    p = self.wallet_plugin_loader(name)
+                    if action == 'restore' or p.is_enabled():
+                        result.append((details[1], details[2]))
+                except:
+                    self.print_error("cannot load plugin for:", name)
+        return result
 
-    def register_wallet_type(self, config, name, x):
-        import wallet
-        x += (lambda: self.wallet_plugin_loader(config, name),)
-        wallet.wallet_types.append(x)
+    def register_plugin_wallet(self, name, gui_good, details):
+        if details[0] == 'hardware':
+            self.hw_wallets[name] = (gui_good, details)
+        register = details + (lambda: self.wallet_plugin_loader(name),)
+        wallet.wallet_types.append(register)
+
+    def wallet_plugin_loader(self, name):
+        if not name in self.plugins:
+            self.load_plugin(self.config, name)
+        return self.plugins[name]
 
     def run(self):
         jobs = [job for plugin in self.plugins.values()