Include seeding time in StatDelta's

[ipsrt]

See #1

[ipsrt]

As per https://github.com/mrd0ll4r/chihaya-privtrak-middleware/issues/1#issuecomment-446549056,

• [x] Change the StatDelta to include a field for continuous seeding time in seconds since the last reported delta.
• [x] Change the userSwarmStats to include a field for seeding time
• [x] Change the update function to track continuous seeding time and emit appropriate deltas
• [x] Change the removeExpired function to emit StatDeltas for userSwarmStats with seeding time != 0. Change all the places calling this to handle the deltas emitted.
• [ ] Add a config key to specify the interval at which seed times are flushed
• [ ] Add a function to flush seed times in one userStats, similar to the GC function
• [ ] Add a goroutine that loops forever and, after each seed-time-flush interval, calls flushes each userStats

Let me know please if I'm on track, or if you're no longer interested in pursuing this project and/or chihaya

[mrd0ll4r]

Hey! Thanks for working on this still :) I'm still interested! I can't be on IRC at the moment because my bouncer is dead, but I'm still interested in chihaya and this.

I haven't looked at the code yet. I'm with my family for a week, next week I can take a look. If you don't hear back from my by mid-next week, please ping me again! Thanks :)

[mrd0ll4r]

Also, in Stop we need to flush the seed times

[mrd0ll4r]

This looks very good! Can you try to figure out a few tests for it?

[mrd0ll4r]

(I want the tests in the same PR, please :) )