examples/nimble_gatt: extend application with ble characteristics
examples/nimble_gatt: extend application with ble characteristics

Extend this application with 2 custom BLE characteristics. One is
read-only and returns a string including a random number and the
second one is writable. In addition, two characteristics for device
information were added (model and manufacturer). Access to the
characteristics produces output on the terminal.

ant9000/RIOT,toonst/RIOT,yogo1212/RIOT,authmillenon/RIOT,aeneby/RIOT,mtausig/RIOT,mfrey/RIOT,A-Paul/RIOT,ant9000/RIOT,authmillenon/RIOT,authmillenon/RIOT,mtausig/RIOT,aeneby/RIOT,ant9000/RIOT,yogo1212/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,basilfx/RIOT,rfuentess/RIOT,basilfx/RIOT,kaspar030/RIOT,lazytech-org/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,A-Paul/RIOT,josephnoir/RIOT,kYc0o/RIOT,authmillenon/RIOT,aeneby/RIOT,smlng/RIOT,x3ro/RIOT,OTAkeys/RIOT,kYc0o/RIOT,cladmi/RIOT,x3ro/RIOT,aeneby/RIOT,smlng/RIOT,x3ro/RIOT,basilfx/RIOT,kYc0o/RIOT,x3ro/RIOT,OTAkeys/RIOT,miri64/RIOT,lazytech-org/RIOT,josephnoir/RIOT,x3ro/RIOT,jasonatran/RIOT,mfrey/RIOT,mfrey/RIOT,yogo1212/RIOT,A-Paul/RIOT,toonst/RIOT,lazytech-org/RIOT,yogo1212/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,mtausig/RIOT,OTAkeys/RIOT,cladmi/RIOT,rfuentess/RIOT,toonst/RIOT,josephnoir/RIOT,authmillenon/RIOT,josephnoir/RIOT,miri64/RIOT,OTAkeys/RIOT,aeneby/RIOT,kaspar030/RIOT,yogo1212/RIOT,kaspar030/RIOT,jasonatran/RIOT,kaspar030/RIOT,A-Paul/RIOT,OlegHahm/RIOT,kaspar030/RIOT,kYc0o/RIOT,jasonatran/RIOT,josephnoir/RIOT,miri64/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,ant9000/RIOT,cladmi/RIOT,miri64/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,mtausig/RIOT,basilfx/RIOT,toonst/RIOT,basilfx/RIOT,A-Paul/RIOT,lazytech-org/RIOT,jasonatran/RIOT,ant9000/RIOT,smlng/RIOT,cladmi/RIOT,mfrey/RIOT,OlegHahm/RIOT,toonst/RIOT,smlng/RIOT,smlng/RIOT,mtausig/RIOT,jasonatran/RIOT,miri64/RIOT,lazytech-org/RIOT,rfuentess/RIOT,authmillenon/RIOT,cladmi/RIOT,mfrey/RIOT