Add a Connect button next to the host field; unwire it from Start

Start/Pause/Stop on the toolbar were never about the websocket
connection - Start now does nothing until that's wired to its own
purpose, and connecting is its own explicit action next to the host
text entry.

client/main_window.py

@@ -1227,6 +1227,9 @@ class Ui_MainWindow(object):
         self.plainTextUri = QtWidgets.QPlainTextEdit(self.centralwidget)
         self.plainTextUri.setGeometry(QtCore.QRect(270, 500, 161, 31))
         self.plainTextUri.setObjectName("plainTextUri")
+        self.btn_connect = QtWidgets.QPushButton(self.centralwidget)
+        self.btn_connect.setGeometry(QtCore.QRect(440, 500, 70, 31))
+        self.btn_connect.setObjectName("btn_connect")
         self.label_8 = QtWidgets.QLabel(self.centralwidget)
         self.label_8.setGeometry(QtCore.QRect(200, 500, 67, 31))
         self.label_8.setAlignment(QtCore.Qt.AlignCenter)
@@ -1291,6 +1294,7 @@ class Ui_MainWindow(object):
         self.label_7.setText(_translate("MainWindow", "State"))
         self.label_state.setText(_translate("MainWindow", "State"))
         self.plainTextUri.setPlainText(_translate("MainWindow", "ws://localhost:8765"))
+        self.btn_connect.setText(_translate("MainWindow", "Connect"))
         self.label_8.setText(_translate("MainWindow", "Host"))
         self.menu_File.setTitle(_translate("MainWindow", "&File"))
         self.menu_Help.setTitle(_translate("MainWindow", "&Help"))