Drag slider for number lineedit in Editor

![urhipullreq](https://cloud.githubusercontent.com/assets/765774/4749886/16ed9126-5a8b-11e4-980b-37d446c61e76.PNG)
I made additional button in Attribute Inspector & Material editor. I dont know what it called, let's say "drag slider". 
Inspiration is from Blender & Unity3D input number field. You can input a number without typing it. Just drag left to decreasing number & right to increasing the number.