Cleanup app.js , make comments and easy to read

[giorgi-ghviniashvili]

app.js got very complex and hard to read, let's try to make it simple, clean and easy to read.

Also @sharlagelfand , have you found out how can we enclose the code in App function, rather than have all props globally available?

[sharlagelfand]

@giorgi-ghviniashvili I think we can try this now - the parent div gets the ID so all of the slider, replay, viz, etc are child divs of it, and so the code will be defined in the parent div and hopefully should be able to access the children just fine? I don't know much about the implementation so the easiest way for me to test is to make everything enclosed and then just try it out!

[giorgi-ghviniashvili]

@sharlagelfand you can take a look (if you would like ofc) at the new code with comments.