Ref #3.  ConstraintHelper.refreshColumnSizes to purge stale column size in case of table def change at runtime.
Merge branch 'master' of https://github.com/ruimo/store
Merge branch 'master' of https://github.com/ruimo/store
merged
Merge branch 'master' of https://github.com/ruimo/store
Merge branch 'master' of https://github.com/snt/store
Cache implementation is switched to scala.collection.concurrent.TrieMap instead of ParHashSet for atomic operation, putIfAbsent.
Ref #7. TrieMap key to use value, TrieMap[ColumnSize, ColumnSize]
Ref #7.
Merge pull request #7 from snt/constraint-helper-con

Constraint helper con