(feat & fix): (1) fix test/axis-break-3.html (2) Add license headers. (3) Fix that axis break should not be a installable "component", but a feature. (4) Make axis break a installable feature, and imported in echarts.all.js and echarts.common.js by default, but not in echarts.simple.js. The zipped size diff is 11KB, not so much but still considerable as a non-common feature.