Do not output exe assembly to bin/Debug folder when working on individual file

[ramon-rocha]

Currently, if a single source file is opened without a project, the generated EXE file will be created in a bin/Debug folder in the same location as the source file.

Ideally, the EXE file should be created in the same folder as the source code file without the creation of a bin/Debug folder.

Note, however, that this behavior would not match the default behavior in MonoDevelop for single source files of other languages, such as C#, which also create an EXE in a bin/Debug folder.