[Refacor] rework plugins within examples/js/plugins folder

[jailln]

Context

Plugins within examples/js/plugins should refactored and updated.

• CSVnVRTParser.js and TIFFParser should at least be rewritten as classes. Also, perhaps the TIFFParser could be added to src/Parser but this is a discussion for another issue.
• FeatureToolTip.js could also at least be rewritten as a class.
• DragNDrop.js could also be rewritten as a class and be added the support of some other format. I think @ftoromanoff previously worked on shapefile support in this plugin.

Motivation

This work is needed to provide users with a harmonized, clean and easy to use plugin package, as discussed in #2197.