Peon can build Townhall from HUD icons
HUD: Delete OrderToGridPos() accessor which is not necessary anymore
UserInput: uses the IsInHUDRegion() on mouse motion event
Somes orders can have an intermediate state to choose destination (move, build)
Build that need a location are rendered
Unit takes time to be trained + unit update take 'curTime' in parameter
UnitDesc: new attribute 'buildTime'
TrainOrder: uses the 'buildTime' attribute from unit description
Update ChangeLog and TODO