Change the field type used for max characters to text

Using a number field type with 'novalidate', there's no way to know if a user has typed text in the field so numeric client-side validation fails.
Server side validation is also not possible because text inside a number input is never submitted.
Add a jsfv type validator for numeric and boolean values
Merge pull request #1405 from akeneo/PIM-2772

PIM-2772 Add client-side validation for max characters attribute property