Template optimizations on version listing

[agjohnson]

Along with a model prefetch change in the view, this reduces the number of queries by 90 queries, from 132 to 42. This:

• Uses prefetch build provided by last_build/latest_build to avoid multiple lookups on Version.build
• Relies on usage of a prefetched project on Version to reduce extra project queries
• Swaps some permission check logic to only perform additional user queries on private versions
• Passes a project object into the build chip to avoid a lookup on Build.project.*

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• Refs #61
• Fixes #463