Deal with multiple statements at once for all kinds of connections

[luisfvieirasilva]

Right now (after this PR is merger) we have three kinds of connections: file://, ws:// and http://. Each one of them has a different behavior when we query multiple statements at once. For instance, if I run select 1; select 2;

• file://: It's just run the first statement and silently ignores the other ones, so just select 1; would be executed. ps: for this one we're using sqlite3 driver.
• ws://: It doesn't accept multiple statements at once and returns an error instead of executing
• http://: It accepts multiple statements, running both select 1; and select 2;. User can call NextResultSet to get all the results.

The idea is to standardized this pattern, following http behavior. That is the closest one to go database/sql standard