Add color variables to input component

[0x80]

I noticed that "blue" is hardcoded into a lot of places in the input component. I've replaced it with "@input-color" and set it to "@accent-1-color". Probably something similar could be done with the "grey" and "red" error colors.

I could make a pull request if you agree with the variable naming.

Slightly related question but really about using Less; is it possible to address only a specific input instance? For example I would like to set @input-width for a search field that's part of a menu/sidebar without affecting the width of inputs I use in other locations. Or would this have to be a component property for it to work?

[hai-cea]

@0x80 Please checkout the TextField component that was just added. It uses the primary-1-color as the underline bar. You also be able to set the width through css. b607a57

[0x80]

@hai-cea That's awesome, thanks!