Added ModifiedOrdersMonitor, added some more doc

MtApi/Monitors/readme.md

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+## Monitors
+
+Monitors can be used to monitor different changes on Mt4 structs.
+
+## MtMonitorBase
+This is the base class for monitoring extensions. If inherited `MtMonitorBase` needs an instance of `MtApiClient` and `IMonitorTrigger`.
+
+`SyncTrigger` (which can be set in the constructor or as Property) can be used to define whether the trigger should be started and stopped as well if `Start()` or `Stop()` will be called on an instance of a child class of `MtMonitorBase`.
+Keep in mind: If an `IMonitorTrigger` will be used for several monitors, `SyncTrigger` set to `true` would cause that all monitors related to this trigger would stop:
+
+```
+var fooTrigger = new FooTrigger();
+var fooMonitor = new FooMonitor(apiClient, fooTrigger, true);
+var barMonitor = new FooMonitor(apiClient, fooTrigger, false);
+
+fooTrigger.Start();
+barMonitor.Start();
+fooMonitor.Start();
+
+fooMonitor.Stop(); //Because of SyncTrigger = true in the constructor of FooMonitor, fooTrigger.Stop() were triggered as well. Therefore barMonitor will not get any further triggers.
+```
+
+## IMonitorTrigger
+An `IMonitorTrigger` is for defining when the monitor should check whether his conditions are met for invoking his event.
+
+There are already two `IMonitorTrigger`s which can be used:
+### NewBarTrigger
+Triggers when a new bar starts
+### TimeElapsedTrigger
+Triggers when a defined time elapsed
+
+## Default monitors:
+There are already two different monitors defined. You can extend them or define new ones by inheriting from `MtMonitorBase`.
+
+### TradeMonitor
+Can be used to get updates on new opened trades or closed trades.
+
+## ModifiedOrdersMonitor
+Can be used to get updates on modified trades (takeprofit, stoploss, operation).
+
+`OrderModifiedTypes` defines which modifications should be monitored:
+
+1. `None` would cause no monitoring. But please use `Start()` and `Stop()` instead.
+2. `TakeProfit` would cause observing whether the TakeProfit were changed.
+3. `StopLoss` would cause observing whether the StopLoss were changed.
+`Operation` would cause observing trades which changed from a stop / limit order to an open order.
+4. `All` would cause observing all above defined.
+
+Because `OrderModifiedTypes` is defined with the Flag-Attribute, you can combine the above monitoring types with a pipe: `OrderModifiedTypes.TakeProfit | OrderModifiedTypes.StopLoss`.
+
+### Example
+```
+var orderModifyMonitor = new ModifiedOrdersMonitor(
+    _apiClient,
+    new MtApi.Monitors.Triggers.TimeElapsedTrigger(TimeSpan.FromSeconds(1)),
+    OrderModifiedTypes.All,
+    true
+);
+orderModifyMonitor.OrdersModified += OrderModifyMonitor_OrdersModified;
+orderModifyMonitor.Start();
+
+private void OrderModifyMonitor_OrdersModified(object sender, ModifiedOrdersEventArgs e)
+{
+    //Receives the event
+}
+```