Smooth Megatools compatibility

[qgustavor]

Some commands aren't implemented:

• [ ] megareg: it's hard to implement: qgustavor/mega doesn't implement it and it would require adding a lot of additional logic;
• [ ] megadf: the basic logic for it is already implemented, but it still can't be used because some bugs;
• [ ] megarm: it seems to be easy to implement
• [ ] megacopy: it seems to be easy to implement
• [ ] megaget: it seems to be easy to implement

Current error handling is by showing a JavaScript error stack trace. As Megatools isn't implemented in JavaScript obviously they handle error in other way. Also contact sharing wasn't implemented.

Megatools will implement sharing features (seems those were already implemented here), file moving, exporting, temporary accounts and other features.

[qgustavor]

No further functions will be implemented.