Error messages and limit = 1

[mcunha98]

During the tests, I saw two problems:

1. The error messages (like maximum number of files selected) is hard coded, it will be good if we can set it via data-attribute or via options.

2. If I set maxFiles: 1 will be good if the dialog window on click to open will be defined as single selection, because don't create the conflict with multiple x not multiple selection