Make easier to check if configuration should be saved

[gmag11]

This implements a flag to let user code to check if configuration has to be saved. This makes possible to work without the need of _savecallback implementation

[gmag11]

If this PR is merged together with #59 a small conflict has to be solved.

<<<<<<< HEAD
		if (!connectedDuringConfigPortal && _savecallback != NULL) {
=======
		_shouldSaveConfig = true;
		if ( _savecallback != NULL) {
>>>>>>> feature/save_config_flag

[alanswx]

do we still need this? sorry i missed it