Rephrased description of cool_min_layer_time_fan_speed_max
Rephrased description of cool_min_layer_time_fan_speed_max

Fixes Ultimaker/Cura#263

senttech/Cura,Curahelper/Cura,ynotstartups/Wanhao,senttech/Cura,markwal/Cura,fieldOfView/Cura,fieldOfView/Cura,fxtentacle/Cura,ynotstartups/Wanhao,fxtentacle/Cura,totalretribution/Cura,hmflash/Cura,Curahelper/Cura,totalretribution/Cura,ad1217/Cura,ad1217/Cura,bq/Ultimaker-Cura,markwal/Cura,bq/Ultimaker-Cura,hmflash/Cura