Storage Node selection improvement

[yasiryagi]

Problem: There is no way to make a storage node higher or lower priority for selection for a new bag.

Current status:

When channel is first created, Atlas selects 4 buckets randomly and assigns to the channel's bag.
When initiating upload from Atlas, all buckets assigned to the bag are sorted by geo distance and tried in that order

Ask:

To add a mean of setting node priority for selection:

1. Manually
2. Automatic base on percentage % usage