Remove ace.dart dependency, use direct JS interop instead

[ahirschberg]

ace.dart hasn't been updated in 2 years, and is very feature lacking. Look into using something like the ace.js typescript mappings + the typescript to dart converter

[ahirschberg]

Also related to #22, relying on the outdated ace.dart got in the way of development. The ace_facade.dart should be much lighter weight and easier to work with / keep updating with ace.js