Effort to update to latest MEGA API changes

[qgustavor]

Since this library is some years old and I haven't made any effort to update it to any changes, I'm sure there are some things to improve.

I'm not checking a lot of MEGA's code in recent months, just testing the library and using it once in a while (mostly using this code I wrote for a private project). Maybe they figured out a way to download things without using HTTPS without making it trivial to find if someone is downloading some previously known MEGA file. IIRC it's possible to edit files by now. I hope they are now using ECDSA instead of RSA to save up a lot of bytes without having to rely on that non-standard encoding scheme they made for RSA which was the root cause of me removing all RSA code from this library (which was only used for ephemeral accounts, yet it could be added back in order to allow user to user sharing).

Is anyone willing to help on this? At least making a list of things that can be improved.

[qgustavor]

MEGA now supports overriding files. I guess from checking developer tools and this code that you just need to upload a new file and put the old file handler in a ov parameter in this object. Can someone test that?

[qgustavor]

Pull request for this feature being drafted here: #214