Add Configuration documentation

Author: Starli0n

README.md

@@ -5,3 +5,42 @@ Archiver dialogs and messages of Telegram (http://telegram.org)
 This project is based on TLSharp (https://github.com/sochix/TLSharp)
 
 ![Screenshot](Screenshot.bmp)
+
+### Configuration
+
+Create the configuration file `App.config` from the template [App.config.tpl](https://github.com/Starli0n/TLArchiver/blob/master/TLArchiver/App.config.tpl)
+
+The proxy settings are defined by the parameters:
+* `HttpProxyHost` (192.168.x.x)
+* `HttpProxyPort` (80)
+* `ProxyUserName` (username)
+* `ProxyPassword` (password)
+
+To obtain your own API id, follow the guidelines of [Telegram](https://core.telegram.org/api/obtaining_api_id)
+* `ApiHash`
+* `ApiId`
+* `SignInPhoneNumberCode` (`+33` for France)
+* `SignInPhoneNumber` (`06xxxxxxxx`)
+Therefore, the number used for the connection would be `+336xxxxxxxx` = `SignInPhoneNumberCode` + `SignInPhoneNumber` without the first `0`.
+
+Enter the code you receive by phone into the GUI and then click on `Login`.
+Therefore let `CodeToAuthenticate` empty.
+
+Set the output directory for the export `ExportDirectory`.
+In `Debug`, this parameter is bypassed by the debug configuration [App.Debug.config](https://github.com/Starli0n/TLArchiver/blob/master/TLArchiver/App.Debug.config)
+
+Set the limit of messages while requesting the server.
+Messages of a dialog are read by packet of `MessagesReadLimit`.
+
+If you want the app to count the messages of all dialogs during the initialisation step, set `CountMessagesAtLaunch` to true.
+However, it will slow down the start.
+
+The configuration is mainly based on the one defined by the [TLSharp](https://github.com/sochix/TLSharp/blob/master/TLSharp.Tests/app.config) library.
+Some parameters are not used in the project, so let them empty:
+* `NotRegisteredNumberToSignUp`
+* `NumberToSendMessage`
+* `UserNameToSendMessage`
+* `NumberToGetUserFull`
+* `NumberToAddToChat`
+
+Note: `NumberToSendMessage` and `UserNameToSendMessage` are used whenever you want to send message with `TLSharp`.