Feature/ble gap device name set

[dangu]

This is a branch aiming to fix the issue discussed in this thread: https://devzone.nordicsemi.com/f/nordic-q-a/71774/device-name-shows-garbage-using-pc_ble_driver_py

Example code: Setting a read-only device name:

ble_driver.ble_gap_device_name_set(name="Joh")

Setting a writable device name:

ble_driver.ble_gap_device_name_set(name="Joh2", device_name_read_only=False)

[dangu]

Please note that this pull request is using commits also in #188