ace.js: prioritize the skin style over the plugin style
ace.js: prioritize the skin style over the plugin style

Preparatory work for introducing colibris skin

aptivate/etherpad-lite,aptivate/etherpad-lite,storytouch/etherpad-lite,joequant/etherpad-lite,ether/etherpad-lite,aptivate/etherpad-lite,cloudfoundry-community/etherpad-lite-cf,ether/etherpad-lite,cloudfoundry-community/etherpad-lite-cf,storytouch/etherpad-lite,aptivate/etherpad-lite,ether/etherpad-lite,joequant/etherpad-lite,joequant/etherpad-lite,joequant/etherpad-lite,cloudfoundry-community/etherpad-lite-cf,storytouch/etherpad-lite,cloudfoundry-community/etherpad-lite-cf