Actually, custom label are not allowed, it directly uses the provided by
the query result as the target/alias
This feature allows to:
- Split YLabel to store its partials and reuse them on link and extra tooltip field
- Override YLabel with splitted and custom values
- Added Extra Tooltip to show metadata to the user on each serie
- use babel to 7, update dependencies, fix#72
- proper babel build to support ngInject, fix#78
- proper buckets display in 6.3.0+, fix#76
- rename js to ts, build d3 lib as js, build src as ts