Angle Markers remain seen

@jonathanolson the little angle line marker things remain after letting go of a mass if the Gravity is min and the Friction is max. This setup ensures that masses have no KE after release:

pendulumlabanglelines

Tested on Win 10 browsers (personal) and iPad 2 iOS 9.2 (Leibniz). For phetsims/tasks/issues/498

Troubleshooting information (do not edit): Name: ‪Pendulum Lab‬ URL: http://www.colorado.edu/physics/phet/dev/html/pendulum-lab/1.0.0-dev.8/pendulum-lab_en.html Version: 1.0.0-dev.8 2016-02-03 23:48:40 UTC User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:44.0) Gecko/20100101 Firefox/44.0 Language: en-US Window: 1600x767 Pixel Ratio: 1/1 WebGL: WebGL 1.0 GLSL: WebGL GLSL ES 1.0 Vendor: Mozilla (Mozilla) Vertex: attribs: 16 varying: 30 uniform: 1024 Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32) Max viewport: 32767x32767 OES_texture_float: true Dependencies JSON: {"assert":{"sha":"d4909677","branch":"master"},"axon":{"sha":"3a5c7fb6","branch":"master"},"babel":{"sha":"cb55342f","branch":"master"},"brand":{"sha":"8c6f9c04","branch":"master"},"chipper":{"sha":"38916c91","branch":"master"},"dot":{"sha":"ddf82014","branch":"master"},"joist":{"sha":"4c228a32","branch":"master"},"kite":{"sha":"4a947119","branch":"master"},"pendulum-lab":{"sha":"07b907c0","branch":"master"},"phet-core":{"sha":"874a703d","branch":"master"},"phetcommon":{"sha":"3db92af3","branch":"master"},"scenery":{"sha":"d0753b38","branch":"master"},"scenery-phet":{"sha":"f02afc1a","branch":"master"},"sherpa":{"sha":"bf82eb95","branch":"master"},"sun":{"sha":"36a0486f","branch":"master"},"tandem":{"sha":"bfd87e0e","branch":"master"}}

phetsims / pendulum-lab

Angle Markers remain seen #139