CarloMariaProietti

Fix #1492 The idea is the following: ValueColumnInternal is an interface for statistic values, which in this way are not exposed as public. Implementations of ValueColumnInternal contain the actual cache....

FIXES #658 It makes possible to compare DataFrame by exploiting Myers difference algotithm whose cost is O((M+N)*D) . M is length of dfA, N is length of dfB, D is...