Invalidate InitializeFeed cache when feed deleted (PR #90)

Re-produce steps:
1. create a 'Data Transformation' feed named foo
2. run the feed 'foo' and wait for it to complete
3. delete the feed 'foo'
4. recreate the feed with the same category and feed names
5. run the feed again

Expected result:
The feed should completed

Actual result:
The feed failed with error says that the 'foo_valid' table doesn't exist

The root cause is that the 'InitializeFeed' processor save the old feed ID in its cache (i.e. FeedProcessor.feedIdCache) and its 'InitializationStatus' in another cache,
but when deleting the feed 'foo', both the feed ID and its 'InitializationStatus' are not removed from the caches.

So when the feed with the same name was created and run, the InitializeFeed processor will get the feed ID of the deleted feed and its 'InitializationStatus' from the caches instead of the ones of the new feed and use it in the following computing.