added media query lines to LayerControl css

Used same concept as in viewer/css/mains.css to adjust font based on screen size
Concept copied from here https://github.com/cmv/cmv-app/blob/master/viewer/css/main.css#L305

My font-size suggestions are only examples taken from my users. Will need to find a good size for various devices if PR is accepted. I received complaints from my users that the screen press on a iPad was not responsive to existing size in v1.3.0