Improve 'send all coins' function:

* do use coin chooser when sending all coins (fixes #2000)
* allow "!" syntax for multiple outputs (fixes #1698)

gui/qt/paytoedit.py

@@ -98,6 +98,8 @@ class PayToEdit(ScanQRTextEdit):
         return script
 
     def parse_amount(self, x):
+        if x.strip() == '!':
+            return '!'
         p = pow(10, self.amount_edit.decimal_point())
         return int(p * Decimal(x.strip()))
 
@@ -138,12 +140,19 @@ class PayToEdit(ScanQRTextEdit):
                 continue
 
             outputs.append((_type, to_address, amount))
-            total += amount
+            if amount == '!':
+                self.win.is_max = True
+            else:
+                total += amount
 
         self.outputs = outputs
         self.payto_address = None
-        self.amount_edit.setAmount(total if outputs else None)
-        self.win.lock_amount(total or len(lines)>1)
+
+        if self.win.is_max:
+            self.win.do_update_fee()
+        else:
+            self.amount_edit.setAmount(total if outputs else None)
+            self.win.lock_amount(total or len(lines)>1)
 
     def get_errors(self):
         return self.errors
@@ -151,12 +160,13 @@ class PayToEdit(ScanQRTextEdit):
     def get_recipient(self):
         return self.payto_address
 
-    def get_outputs(self):
+    def get_outputs(self, is_max):
         if self.payto_address:
-            try:
+            if is_max:
+                amount = '!'
+            else:
                 amount = self.amount_edit.get_amount()
-            except:
-                amount = None
+
             _type, addr = self.payto_address
             self.outputs = [(_type, addr, amount)]