Save path from path edit

[fluxxcode]

When the dialog is in file save mode, the path edit is used as the expected file to save if:

• an extension is specified,
• the path is not an existing directory,
• and the parent path exists.

Closes #159

[crumblingstatue]

I personally want to be able to create files even if they don't have an extension. My hex editor that uses this wants to be a tool useful in as much contexts as possible, including dealing with files without extensions. I agree that it can be confusing if the user mistypes a directory in the top bar, and it saves instead of erroring, but there should at least be an option to enable this behavior.

[fluxxcode]

Ye, that's what I thought. It's confusing both ways. If the dialog saves an incorrectly typed directory, but also if the dialog saves a file entered and sometimes not. \ I think an option in the backend is a good idea.

[crumblingstatue]

I'll leave it up to you whether this should block the PR or not. I can open a separate issue for the extension question, if you'd like. Edit: Never mind, I just saw you added an option

[fluxxcode]

Implemented the option allow_path_edit_to_save_file_without_extension. Let me know if you have a better name for it ^^ I'm just not sure if this should be enabled or disabled by default. I think it is less confusing for the user if a misstyped directory is selected as a file by default.

[crumblingstatue]

I'm fine with it being disabled by default. I just need it for my power-user oriented application. I tested the option, and it works fine, thank you!

[fluxxcode]

Then I'll merge it now. thanks for testing!