Update new button from font element to SVG element

[skullbunnygalaxy]

From @LuxBrush:

we should change the plus in the new button from a font element to an SVG element. Having it as a font-based element makes its position too inconsistent across browsers and operating systems. I noticed this today as I was using the website on Windows and my Chromebook.

Going to implement one of the font awesome icons for this with the m-auto class.