Added 'Overwrite Files' Checkbox to Give Users the Option of Overwriting Existing Files During Upload

[uwecmyersjj]

This would be an optional checkbox users could choose to use in the case they want to overwrite uploaded files if there is already one that matches the same filename.

[ner00]

Haven't tested this, but in theory it's a worthwhile addition.

Just a nitpick: keep the code formatting in line with the current style, for example:

if ($overwrite_files == 'Y') {
    $fullPathTarget = $path . '/' . basename($fullPathInput, $ext_1) . $ext_1;
} else {
    $fullPathTarget = $path . '/' . basename($fullPathInput, $ext_1) .'_'. date('ymdHis'). $ext_1;
}