Add option to set the default isolation level for the connection

We have a requirement that all queries use `READ UNCOMMITTED` by default. This PR adds an option, `connectionIsolationLevel`, that allows setting the isolation level in the initial sql batch that gets sent when a connection is opened.

Also, I noticed that using the single quoted block string was causing the newline to be trimmed, resulting in the wrong sql being sent

```sql
set textsize 2147483647set quoted_identifier on
```

instead of

```sql
set textsize 2147483647
set quoted_identifier on
```

Changing the batch to use a single double quoted block string and using coffee scripts interpolation fixes the issue.