Partially reverts 2fa86c361b88fbd4c36adaad60be2104e57d75f5. The commit introduced a regression such that RailsAdmin::Config::Model#excluded? stopped caching false values.
Coverage: 95.911% (+0.001%) from 95.91% when pulling 856758a5b5c304acc333dd549c6ed5ff7fd71d92 on jdufresne:restore-caching into e8319bc5130c9fff31229827b5741a3707e6dc9d on railsadminteam:master.
Partially reverts 2fa86c361b88fbd4c36adaad60be2104e57d75f5. The commit introduced a regression such that RailsAdmin::Config::Model#excluded? stopped caching false values.