Allow execution of non-local executables

Allow execution of executables/scripts which are not in PATH. A possible option would be to still use the @-sign but the path to the executable is specified within quotes. E.g.

```golang
@"localPath/test.bat"(arg1, arg2)
```

Or probably in round brackets or something similar.

```golang
@(localPath/test.bat)(arg1, arg2)
```