Multiple problems and suggestions

Hello,

i am testing your plugin and came across several problems and suggestions:

• The unit name inside input fields is not centered vertically like the input values (the unit name is too low)
• When showing the input value on the product image, the unit name is already shown on the image even when the input field is empty and you haven’t entered a value yet
• When using required input fields with min and max values and you leave these blank and press the Request a quote button, there is only an error message below the field. The border of the field should be red like if you input a value which is not between min and max
• When showing the price difference of an attribute option, the difference is only shown for attributes which have a price. Example: Attribut material: plastic has no price, steel +10.00. if you select plastic, steel shows with +10.00. But if you choose steel, plastic show with no price instead of -10.00
• Please add an option to show the form shortcode in a popup and not only below the quote button
• Add an option to change the border color of fields for different states (active, hover etc.)