update TODO file

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@917 d9718cc8-9f43-0410-858b-315f434eb58c
docs: add inline documentation for various Sprite classes

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@918 d9718cc8-9f43-0410-858b-315f434eb58c
docs: document the Tiles class

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@919 d9718cc8-9f43-0410-858b-315f434eb58c
docs: document the CityRect class

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@920 d9718cc8-9f43-0410-858b-315f434eb58c