host: possibility to change seating

[tooomm]

A host should be able to swap the position of players before the draft starts (with little arrows for example).
This would allow for easier team drafts which have a fixed seating.
Also, when an external site/service requires a specific player order for example or there is any other reason you want to influence things (redo a draft with same order...) it would be nice to be more flexible.

[tooomm]

#33 adds initial support for this 👍

Some issues still stand with that implementation:

1. What I miss there is, that once a host start swapping people around with the arrow buttons, shuffle should get automatically checked and disabled to make sure his preferred seating order isn't mixed up again!

2. Regarding the swapping buttons itself:
   Since you can't cycle a player on position 1 to the bottom if you hit up, It would be clearer to disable/grey out up for the first player, and down for the last.
   You can hit those buttons but just nothing happens currently.

I think we also talked in gitter chat about the last one and said that cycling players from 1 "up" to 8 would also be very nice. So it's either of those: Allow cycling or disable up/down buttons on first/last position. I prefer cycling since it's more intuitive.