Automatically set width/height/left/top/right/bottom constraints on some elements
When using a symbol from the sketch-file it should be possible to change the size of it without it getting distorted.

![45805912-0d703400-bcc0-11e8-99b7-eb5f59a0e061](https://user-images.githubusercontent.com/1714029/45811834-78c10280-bcce-11e8-8497-9fad00747627.gif)
