Improve error messages in REPL by printing and underlining failed line of code

[drognanar]

When parser fails it prints the error along with the location of failures. The REPL does not underline this location making it hard to locate the problem. For instance given the following submissions:

> public class MyClassA {}
> public class MyClassB : MyClass A { }

REPL will print the following error:

(1,33): error CS1003: Syntax error, ',' expected

The following error message would be more readable:

public class MyClassB : MyClass A { }
-------------------------------^-----
(1,33): error CS1003: Syntax error, ',' expected

[tmat]

This can get complicated with multi-line input. Perhaps we could use Console API to highlight the error locations (dark-red background color or light-red foreground color)?

[tmat]

Also note that VB compiler prints out ~~~ for errors. That could also work in REPL, although it makes the output longer since we need to echo the lines that contain the errors.