Fixes #405 - added isFlingEnabled setting

[lesniakania]

PR Checklist:

• I have tested this extensively and it does not break any existing behavior.
• I have added/updated examples and tests for any new behavior (there are no tests/examples for similar things e.g. isDragEnabled so I didn't add mine too).
• If this is a significant change, an issue has already been created where the problem / solution was discussed: [N/A, or add link to issue here]

PR Description

This adds isFlingEnabled setting so onChartFling can work properly.
Fixes #405

[Paget96]

I really like this library and using it in my apps, I would like to call people to continue with this awesome thing. I have forked the repo and started working on it! So I am ready as well to accept pull requests, I'll notify other people from here as well!
Would be more than happy if we continue with this awesome project.

Code is full kotlin now!

Make your pull requests here:
https://github.com/Paget96/MPAndroidChart

[PhilJay]

Thanks a lot for this pull request, and sorry it never got merged. MPAndroidChart 4.0.0 is a complete rewrite in Kotlin (https://github.com/PhilJay/MPAndroidChart/releases/tag/v4.0.0), so this change no longer applies to the code base and I am closing it. If it is still relevant for 4.0, a new pull request against master is very welcome. The Java 3.x code lives on in the 3.x branch.