add configuration_over_nimble application

[HendrikVE]

This application provides a simple Bluetooth LE service (via RIOT's NimBLE port) for device configuration purposes. The included bluetooth characteristics are taken from an application for a sensor node, which is placed in a specific room and transmits data to a MQTT-SN gateway.
The sent values ​​are stored persistently in MCU's internal flash via RIOT's flashpage API.

There is an Android App specifically written for this application. Either build the app yourself from source,
download it from here or use Nordics "nRF Connect"-App, available for Android and iOS.

In the case you want to use Nordics app, you will need to write an empty string to the characteristic "890f7b6f-cecc-4e3e-ade2-5f2907867f4b" in the end of the configuration process to store the data permanently and to restart the device afterwards.

Currently the application is only running on nrf52dk and nrf52840dk boards.

Clean install

Add JLINK_PRE_FLASH=erase to your make command to erase the flash memory. That way you avoid data left in the storage, especially on the flash page used for configuration.

[smlng]

a first general comment: the name configurator is too generic, hence I would suggest to make it more specific, e.g. adding ble as prefix?

[HendrikVE]

a first general comment: the name configurator is too generic, hence I would suggest to make it more specific, e.g. adding ble as prefix?

Yes, you are right. I would say that configuration_over_nimble might be even better, as the implementation is bound to nimble.