Sync command should support resuming a SyncSession through ID argument

[bjester]

Background

The sync management command doesn't currently support resuming a sync session, so if synchronization becomes interrupted for any reason, you must start from scratch to complete the transfer.

User story

As a user who is using Kolibri's sync command in connectivity challenged environments, I need to be able resume a sync if it is interrupted. Syncing large amounts of data can take some time, especially on slower connections, and if that becomes interrupted, I'm faced with having to restart the entire process which leads to a loss of time and perhaps increased cost from the data transfer.

Deliverables

• The sync command should update its task state with the SyncSession ID when it has created a new session to allow for resuming a specific interrupted sync task through the UI
• The sync command should accept a --syncsession_id argument and should pass it to resume_sync_session