Write all VTY commands in monospace and add configuration example
blocks. Add an example VTY session for enabling CS and PS NAM.
Realted: OS#2542
Change-Id: I54f80810db3dac7a4a56ad42c5d2154b6006108c
Add a new section in the subscribers chapter, with detailed explanation
of the use cases and related OsmoHLR and OsmoMSC configuration.
Related: OS#2542
Change-Id: I2dd4a56f7b8be8b5d0e6fc32e04459e5e278d0a9