This class provides an advanced file uploader system for file uploads made from
html forms.

Features:
-  Can handle from one file to multiple files.
-  Safe file copying from tmp dir.
-  Easy detecting mechanism of valid upload, missing upload or error.
-  Gives extensive information about the uploaded file.
-  Rename uploaded files in different ways: as it is, safe or unique
-  Validate allowed file extensions
-  Multiple languages error messages support (es, en, de, fr, it, nl, pt_BR)