Revert "Revert "Accept `dbname.tablename` style for the argument of `tbl()`""
Revert "Revert "Accept `dbname.tablename` style for the argument of `tbl()`""

This reverts commit 9742ac418319cb922c7985f1caf85190ef4e02e3.

rstudio/sparklyr,kevinykuo/sparklyr,rstudio/sparklyr,rstudio/sparklyr,rstudio/sparklyr,kevinykuo/sparklyr,kevinykuo/sparklyr,kevinykuo/sparklyr