Add Jellyfish weapon

[64kramsystem]

This weapon turned out to be complex, not in algorithmic terms, but in terms of states handling and general coupling.
Additionally, it will likely require tweaking once it's decided how certain aspect should behave (for example, should the floating JF always move sideways if there is no space to jump?).

There are two global changes in this PR:

1. Addition of the remote_control field to the player, which disables the input when set
2. Made Input and its fields public; this allows weapons to poll the controls, without the Player type being aware of the weapon

With a better knowledge of the project and/or MQ, there may be simplifications.

A design choice has been to handle all the state logic via Jellyfish methods; if that logic is spread out, it may be very messy to track.

jellyfish.mp4