Misc. small changes

* Fixed typo: Renamed `BoxFoldersManageImpl` to `BoxFoldersManagerImpl`.

* Changed some constants in `BoxConfigBuilder` from private to public
  (useful if someone wants to implement `IBoxConfig` on their own, but
  wants to use some of these default values).

* Changed `BoxConnectionManagerBuilder` so that all time arguments are
  in milliseconds, rather than some being in milliseconds and others
  being in seconds.

* Changed the order of method definitions in `IBoxConfig` so that
  related methods are grouped together.