Should lookups be split out or otherwise disabled by default?

[Matt Sicker]

For the extra paranoid users and users who already use some other method of 
generating config files (e.g., using the ConfigurationBuilder DSL which already 
supports arbitrary Java code), it seems like a useful feature to make lookups 
an opt-in feature. What do you all think? Any splitting from core would need to 
be done for 3.x, though we can add @RequiredProperty annotations to StrLookup 
plugins in 2.x to make a similar change.
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Matt Sicker