Check if Dropbox, Box, Google Drive can accept upload

[jgoldverg]

Feature: Google Drive, DropBox, and Box all have total byte limits.
Say a given user can store 1GB on google drive and they want to send 2GB to their google drive account. The Transfer-Scheduler needs to check if the account can handle the amount of data added with the given request.

This way no transfer that fundamentally will fail will not happen at all.

A way to implement this is to create another interface called checker that the current implemented Expanders can implement and then use the already created client in the Expanders class to then check if the account can handle this.