Refactored UnconsumedFeedEntriesFinder (now AvailableFeedEntriesFinder) to add the resource-link to the tracker
Removed underscore from test names
Added test for FeedTracker.track simpleDB implementation; changed AvailableFeedEntriesFinder#isTracked to return true rathen than false
Changed AvailableFeedEntriesFinder, updated FeedConsumerConfiguration and FeedConsumerScheduler

- AvailableFeedEntriesFinder: expects feedEndpoint as constructor parameter rather than method parameter. Now it will be run
  regularly by the scheduler and it's more convenient to encapsulate the feed-endpoint in it
- FeedConsumerScheduler: expects a feedEntryFinder. It will run it using the same interval of the consumer, but earlier.
- FeedConsumerConfiguration: now instantiates the scheduler providing a feedEntryFinder
Updated FeedConsumerSchedulerTest