Proper overview and towers split.

- Overview returns reinforced and low fuel towers.
Ensure resources updated correctly.

- Turns out an explicit value of 0 was assumed to be missing.
EVE API does not supply value of 0 if missing

- So for cases where a pos went into reinforcement the strontium amount
  was not set correctly.  So yet another flag is provided.
More attributes to the tower

- The tower json output now also provide the state timestamps.
Allow the logging of usage of API keys

- This can be used by the manager to note down when the requests were
  done.
Helper for import from Corp API

- Would be nice if I had added some tests...
I think I went insane two commits ago.

- Really I don't know what I was thinking, I think I was thinking append
  instead of update.
- This is more sane.
- Oh yeah, this does let users easily figure out which towers have been
  updated from which hasn't been even if multiple API keys return the
  same towers.  Well I need to test that, do I?
Method for fetching tower ids that hook into API.
Include the API timestamp.
Track the API times from the manager.
Report previous API update time.