ENG-4582 Get the Site plan cache to retain recent ad hoc fragments.
ENG-4582 Extensive rework to Site's LRU fragment eviction re: review feedback
Merge branch 'master' into ENG-4582-adhocperf
Merge pull request #475 from VoltDB/ENG-4582-adhocperf

ENG-4582 Get the Site plan cache to retain recent ad hoc fragments.