mesh: move gatt services into mesh/gatt-service folder

Merge branch 'develop'

# Conflicts:
# README.md

example/hid_keyboard_demo: queue keys via ringbuffer

example/hfp_ag_demo: request master role on reconnect

example: use sm pairing events instead of hci encryption change (v2)

example: handle HCI_EVENT_ENCRYPTION_CHANGE_V2

example/sine_player: add option to set num channel

example/sco_demo_util: drop ENABLE_SCO_STEREO_PLAYBACK code

example/spp_counter: use snprintf

Merge branch 'develop'

example/hfp_ag_demo: add commands for initiating and establishing outgoing call

example: fix warnings

example: use snprintf

windows: ignore deprecated warning for fopen

example/a2dp_sink_demo: don't store sbc data in file

example: avoid HCI_EVENT_IS_COMMAND_COMPLETE macro

example: fix warnings

example: CMakeLists.txt provides list of examples separated by Bluetooth mode

example/hfp_hf_demo: print alpha CLIP alpha field

ports: add a2dp

example/a2dp_sink_demo: clean up debug output

example: allow role switch in a2dp_sink_demo and hfp_hf_demo

Merge branch 'develop'

# Conflicts:
# CHANGELOG.md

example/pbap_client_demo: print operation complete status

example/hfp_ag_demo: print microphone and speaker gain