Add date_trunc function to mysql#17

Open

andresgutgon wants to merge 2 commits intot27duck:masterfrom

andresgutgon:feature/trunc-date-mysql-function-implementation

Commits on Oct 15, 2018

Implement database adapters to be able to have diferent ways of implementing the same feature
andresgutgon
committed
Fixed bug introduced on PR: 16
andresgutgon
committed