Refactoring to use Map to build chart options and data.

[dyorgio]

Stop to work with elemental json lib and start to use plain java.util.Map because elemental don't support a function or raw js object in JsonValue.

Implemented userCallback in Ticks.

#39 #38 (initial work)

[moberwasserlechner]

I appreciate your effort but It would have been nice if you first discussed your planned changes here rather than changing half of code base. Anyway I'll try to review it on the weekend.

[dyorgio]

@moberwasserlechner, you are right, I think a lot before start to do this modification, it is really impact in all codebase. But, after try many times to make it works with elemental (because I need to pass a JS function to chart) I only found this solution. I believe that this functionality is very important to support customizations and plugins. Tks for getting time to review it :).