Relax groups and blocks to output at pipeline level

[sophiajt]

This PR does a few things:

• it relaxes the redirection in blocks. This allows you to run commands that use interaction in a block. For example, this would now work:

do {
  vim
  echo done
}

• Treats ; as equivalent to carriage return in source code. That means that:

echo hello; echo world

would be equivalent to:

echo hello
echo world

Taken together you, can rewrite the first example as:

do { vim; echo done }

• To get the old ignore behaviour in some form, I added an ignore command. You can pipe to this command, and it will drain the stream and not output anything.

autoenv trust foo | ignore

I also went ahead and cleaned up a bad external arg error to be a little less bad.

[andrasio]

I don't understand this example.

[sophiajt]

Lolol I put the sample in the description instead of where it should go. I'll fix it