Save and load feature

Yello,
something important that was still missing from the game was saving and loading. I thought serializing (i.e. convert data in a saveable format) would be difficult, since I never had the problem of saving data this way, instead I found it's pretty easy and straightforward to do.

It need some more testing in order to understand if I actually save all the data needed by the game, but other than the save and load feature are completed! YAY!