fix shapeshifter gomobile builds for Android...

... by renaming ShapeShifter struct to Shapeshifter

This MR fixes building shapeshifter go lib. Even though this lib is going to be replaced, it can be optionally used instead of obfsvpn in Bitmask Android and its custom branded versions.

Not sure if Bitmask Destop is still using shapeshifter at all. we then may to adapt a little bit of code there as well.