Harden "Depends on" predicates

[rbrewer]

Currently, the Depends on predicate for activities is fragile: any error in the predicate (like a typo) leads to the SGG generating a 500 error. I propose two solutions to "harden" the predicates:

• Make the SGG more resistant to errors. If a predicate cannot be evaluated for some reason, just make that cell locked but continue to render the page.
• Verify that the predicate can be evaluated in the admin interface before allowing the user to save changes. This is already done for quests.

[yongwen]

migrate to makahiki2 in csdl repo.