Semicolons should be required regardless of Multiline

Hello,

First of all, thank you for all your work on this tool :)

It was not immediately apparent to me moving from `psql` that hitting `return` would immediately execute the query without a semicolon. Given https://github.com/dbcli/mssql-cli/issues/175 , it appears that multi-line mode will end with a `GO` rather than a semicolon. I recommend altering tool behavior to not execute the query unless a semicolon is present.

--- An extended explanation follows ---

The tool behavior as it stands prevents a minor inconvenience (needing to enter a semicolon.) The tool behavior as recommended by this issue prevents potentially destructive accidental usage by novice and expert users alike.

For reference, a simplified example of a recent mistake I made, expecting to be protected by not yet typing a semicolon. When typing the final single quote, the return key was accidentally pressed by the same finger:

```
update comments set comment = ''
(11639 rows affected)
Time: 0.253s
```

The query would have been:

```
update comments set comment = 'something' where id = X;
```

I ended the string in order to write the `WHERE` clause so I wouldn't forget and accidentally update every row in the database. Obviously I was horrified that I ended up still updating every row in the database.

For now I can set Multiline to enabled since I now understand the nuances of it's behavior. Unless this issue is accepted, I'll also be leaving it on after issue 175 is completed, and writing `GO` after each line.

Thanks again!
Josh