Blurry fonts due to lack of anti-aliasing options

## Problem

On my low resolution (1366x786) and low quality lcd display, fonts with grayscale anti-aliasing look blurry. However setting antialiasing to rgba using dconf-editor makes them smoother and more readable.

## Proposal

Allow changing anti-aliasing type from the appearance plug. There have been some complaints about blurry fonts since the switch to inter. I thought it was the same for me but it turned out to be related to anti-aliasing. Perhaps this would help such users as well