Multi-part column names and sign related fixes

The patch contains two fixes:
1) Corrected Sql Server multi-part column names (schema.table.column) in the select statement to accept empty table name;
Accommodated the Table#getWholeTableName function;
2) Corrected the signed expression behaviors and renamed InverseExpression to SignedExpression;
Renamed S_INTEGER to S_LONG;
Added tests for signs;