SettingsWallet: lock wallet on demand

This commit adds the ability to lock the wallet on demand instead
of waiting for the user inactivity time out. It is binded to the
hot keys Ctrl+L. Pressing cancel or the esc key will send the user
back to the wizard home for wallet selection. Incorrect password
returns the error message. Correct password will remove the
PasswordDialog allowing access. Add lock functionality in the
wallet settings section and title bar.

pages/settings/SettingsWallet.qml

@@ -50,6 +50,14 @@ Rectangle {
         anchors.topMargin: 0
         spacing: 0
 
+        MoneroComponents.SettingsListItem {
+            iconText: FontAwesome.lock
+            description: qsTr("Locks the wallet on demand.") + translationManager.emptyString
+            title: qsTr("Lock this wallet") + translationManager.emptyString
+            symbol: (isMac ? "⌃" : qsTr("Ctrl+")) + "L" + translationManager.emptyString
+            onClicked: appWindow.lock();
+        }
+
         MoneroComponents.SettingsListItem {
             iconText: FontAwesome.signOutAlt
             description: qsTr("Logs out of this wallet.") + translationManager.emptyString