Make the telnet example an Lua module (#3133)

Also update ftp server

Author: marcelstoer

docs/lua-modules/telnet.md

@@ -0,0 +1,50 @@
+# Telnet Module
+
+| Since  | Origin / Contributor  | Maintainer  | Source  |
+| :----- | :-------------------- | :---------- | :------ |
+| 2018-05-24 | [Terry Ellison](https://github.com/TerryE) |  [Terry Ellison](https://github.com/TerryE) | [telnet.lua](../../lua_modules/telnet/telnet.lua) |
+
+The current version of this module exploits the stdin / stdout pipe functionality and 
+task integration that is now build into the NodeNMCU Lua core. 
+
+There are two nice advantages of this core implementation:
+
+-  Errors are now written to stdout in a separate task execution.
+-  The pipes pretty much eliminate UART and telnet overrun.
+
+Both have the same interface if required into the variable `telnet`
+
+## telnet:open()
+
+Open a telnet server based on the provided parameters.
+
+#### Syntax
+
+`telnet:open(ssid, pwd, port)`
+
+#### Parameters
+
+`ssid` and `password`.  Strings.  SSID and Password for the Wifi network.  If these are
+`nil` then the wifi is assumed to be configured or auto-configured.
+
+`port`.  Integer TCP listening port for the Telnet service.  The default is 2323
+
+#### Returns
+
+Nothing returned (this is evaluated as `nil` in a scalar context).
+
+## telnet:close()
+
+Close a telnet server and release all resources.  Also set the variable `telnet` to nil to fully reference and GC the resources.
+
+#### Syntax
+
+`telnet:close()`
+
+#### Parameters
+
+None
+
+#### Returns
+
+Nothing returned (this is evaluated as `nil` in a scalar context).