Data validation class

This class can perform several types of validation of text values. It can:

- Check if a number is between a minimum and a maximum value
- Check if an e-mail address is valid
- Check if an URL is valid
- Check if an IP address is valid
- Check if a string address is alpha-numeric or contains a range of characters
- Check if the length of a string is between a maximum and minimum length
- Check if the size of a file is between a minimum and maximum length
- Check if an image file has a size between a minimum and maximum width and height