behaviors: move exploding-tile processing to new TileBehavior-based class

git-svn-id: http://micropolis.googlecode.com/svn/trunk@872 d9718cc8-9f43-0410-858b-315f434eb58c
refactor: make accessor method for fireRate[] array

git-svn-id: http://micropolis.googlecode.com/svn/trunk@873 d9718cc8-9f43-0410-858b-315f434eb58c
cleanup: move code that refreshes tile/rawTile closer to where it is needed

git-svn-id: http://micropolis.googlecode.com/svn/trunk@874 d9718cc8-9f43-0410-858b-315f434eb58c
refactor: move makeTraffic() from city to zone-behavior class

git-svn-id: http://micropolis.googlecode.com/svn/trunk@875 d9718cc8-9f43-0410-858b-315f434eb58c