Replacing old doc/figs/configuration/configuration-game-admin-smartgrid-designer-new-level.png with image that shows "Unlock condition" field.
doc/challenge-design-game-admin-smartgrid-game.rst: Corrected to state that level name and an unlock condition are required to create a new level.
challenge-design-game-admin-resource-game.rst, challenge-design-game-admin-smartgrid-game.rst: Fixed typos noted by ICS 691 Spring 2013 students in past survey.
doc/challenge-design-game-admin-resource-game.rst: Edited "From Energy Goal Games to Resource Goal Games" to indicate that support for the water game is enabled by default.
doc/figs/configuration/configuration-game-admin-smartgrid-designer-new-level.png: New image has smaller file size (previous one was badly converted and > 1.74 MB).
Merge pull request #565 from jtakayama/master

Fixed an outdated image, incorrect documentation for the Water resource game, and some typos.