Revert "Fixes in Dropbox API, try to catch Dropbox exceptions, implement rename and copy in Dropbox storage backend"

This reverts commit ea9b7206775d24929b9df779e62dd920a08f4a9c.
Revert "Bump Dropbox-PHP to version 1.0.0"

This reverts commit 490578ba4b6e16fb6f21e0c9daaff4a0f7d1662f.