Uploading autorized and non-autorized file extensions

[matwachich]

Hi, and thanks for this library.
Example:

• I set an upload form with only image files autorized (jpg, png, gif)
• I try to upload... say a .jpg file and a .ini file.
• I have the error message "upload_invalid_filetype", and no upload_data array, as expected.
• But the problem is that the .jpg file is actually uploaded!

The correct behaviour is:

• Either do not upload (or delete uploaded files) any file if one of theme is of incorrect type (extension, big size ...)
• Or, fire the error message for individual, incorrect files, and return a upload_data array for the correct ones

Thanks :)