Implement Sleeping

[Gvin]

The player should be able to sleep in his Camp. Sleeping replenish Energy stat. The player can select how much he is going to sleep (hours).
Having some buildings should affect sleep effectiveness (better house, better bed).
Weather also affects sleep effectiveness: better sleep on rainy weather, worse sleep when it is hot or cold.
Some buildings can negate weather effects (having campfire and bed partially negates cold, having good house and water evaporation cooler partially negates hot).