Add 2 new roles: doctor and alpha wolf

Doctor is on the village team, and has a number of immunizations they
can give out during the day. An immunized lycan reverts a normal
villager, and anyone that is immunized will die instead of turning into
a wolf if they are bitten by the alpha wolf. Beware, however, because
attempting to immunize someone already bitten will simply speed up the
process of them becoming a wolf!

Alpha wolf has a once-per-game ability where they can bite the wolves'
target instead of killing them following the death of a werewolf during
the day. The bitten person will subsequently turn into a wolf in 3
nights.
Make alpha wolf more powerful

Each time a wolf dies while a bitten person is undergoing
transformation, they will now transform one night earlier. This makes it
much more likely for the bitten person to actually turn into a wolf
before the game is over. For larger game sizes, the turn is pretty much
guaranteed due to the number of wolves, which means safes need to
tightly coordinate to figure out who was actually bitten due to wolves
possibly having full info and an insider.
Make the bite command make use of the new get_victim function
Add "alpha" gamemode

This mode features the alpha wolf and doctor roles, and should provide
for very "swingy" games where wolves are very disadvantaged at first
but should be able to make a decent comeback later on.

This also brought some rebalancing to gamemode weights, mostly all of
the existing ones stayed the same though, a summary of changes is below.
Numbers below are rounded to the nearest percent, so they won't
necessarily add up to 100.

default: 41% -> 40% (-1%)
foolish: 19% -> 16% (-3%)
mad: 19% -> 16% (-3%)
classic: 11% -> 8% (-3%)
lycan: 3% -> 2% (-1%)
aleatoire: 8% -> 8% (0%)
alpha: n/a -> 10%
Merge pull request #98 from skizzerz/alphawolf

Add 2 new roles: doctor and alpha wolf