updating wasp attack routines and picnic health mechanic

Wasps can now eat the picnic (dealing small damage rapidly to the picnic
health), as well as repeat damage to player/spouse at ~1.5 second
intervals.

Picnic health is no longer pool of food and spouse, it is single value
and attacks to picnic/spouse deplete it. Game fail state when picnic
integrity reaches 0%, and UI picnic health UI displays failure message.