This commit introduces Common::CloudManager, which can be accessed from
OSystem.
The backend for this manager is Cloud::Manager (defined in
backends/cloud/manager.h). It should load all users storages from
configs and provide access to current Storage instance. For now it just
creates a new one.
Cloud::Storage (backends/cloud/storage.h) provides an API to interact
with cloud storage, for example, create new directory or sync files.
Right now it's not ready and has only two dummy methods: listDirectory()
and syncSaves().
There is Cloud::Dropbox::DropboxStorage backend
(backends/cloud/dropbox/dropboxstorage.h) for Cloud::Storage. Right now
it implements both listDirectory() and syncSaves() with starting timer
task and handling it by printing out some JSON examples.
