Added first information about reference toolchain (thx to mmk).

manage-networks/yangnmi-prog/README.md

 # Programming with YANG and gNMI
 
 This section introduces how to use yang modules and gNMI together. All examples here are based on the go programming language, ygot, openconfig's gnmi and yang modules. 
+
+## Reference Toolchain
+
+The reference toolchain for the practical exercises is this
+
+| Technology | Reference | Version | Mandatory |
+| --- | --- | --- |  --- |
+| Programming Language | go | 1.14 | Yes |
+| yang toolkit | [openconfing ygot](https://github.com/openconfig/ygot) | see go.mod files |  Yes |
+| gnmi toolkit | [openconfig gnmi](https://github.com/openconfig/gnmi/) | see go.mod files | Yes |
+| operating system | [FreeBSD](https://www.freebsd.org) | see Section XXXX | No, can use other OS |