REPL vs File execution

[mbmcmullen27]

We're printing all expressions still when we execute a file, this works how we expect when we're actively typing in the REPL, but when run from a file output is not what we expect.

• this was a challenge implementation from an earlier chapter
• need a mechanism to know whether or not we're executing from a file. (runFile() method is a good candidate)

java com/craftinginterpreters/lox/Lox tests/while

testfile prints numbers 1-10

while (x<10)
{ 
    x = x+1;
    print x;
}

[mbmcmullen27]

Closer to an implementation that works with this commit, we detect when we're called from a file and set a public static var in the interpreter before we execute.
b077953

HOWEVER...
that doesn't get us all the way, we don't print anything for statements, consider JS console will print undefined for var statements, and we still print twice in the example loop above. We should consider extending this to only print the resulting expression or last expression instead of every expression, OR no printing when you're inside a block statement. I think the former is what most interpreters do.