Changing NERC & ECs

The obtained NERC, doesn't matter the way, can be changed by ECs that can be used to make all types of buys inside the Nergame platform, like participate in the events, complete the daily challenges, etc.

Also, all the ECs won by the users can be exchanged by NERC at a rate of 150 ECs = 1 NERC. This rate can be changed a little bit (-+ ~15%) in the future to ensure good sustainability.