Switch to AP Mode without Reset

[FordPrfkt]

Since the only free button on my node is already used to switch to flash mode during reset, i would like to have a feature that allows switch to AP mode after start by a long press of AP_ENABLE_BUTTON.

I'll implement this and open a pull request to pull the feature in if you like it.

[FordPrfkt]

Reconsidering my idea i find this unsafe. Someone could use this to get the wifi credentials and other network data. The point of this was to re-gain access to the device if i ever forget the login data.
So i'll rather implement a function that allows clearing all the configuration data and the secret.json and resetting the device. This will put it back to "factory" mode and allow me to reconfigure it.