Restructuring the repo

[gnz00]

Wanted to add some sensible structure and organization going forward.

I threw this together, currently using it in my app and all tests are passing:
https://github.com/maysale01/parse-server/tree/restructuring

[gfosco]

It is definitely prettier that way... Will consider making these changes over the next few days.

[drew-gross]

This has been done now.