ENG-4848 Base script for profiling snapshot performance.
ENG-4848 Add zoom profiler support.
ENG-4848 Handle empty predicates to avoid excess eval's
ENG-4848: Don't create dummy predicate for snapshot data targets that want
everything.
ENG-4848 Short-circuit empty expression evaluation.
ENG-4848: Don't put the predicate expression key in the JSON object if there is
no snapshot predicate expression.
ENG-4848: Remove unused imports from SnapshotPredicates.
ENG-4848 Tweak empty predicate format.
Merge pull request #618 from VoltDB/ENG-4848

ENG-4848 Elastic snapshot impact profiling and fix