New Feature: Blog Trigger or Storage Queue Trigger on File Deletion

Add a blobTrigger or Storage Queue trigger on File deletion. For this to be useful, you'd also have to implement #1611 so it was possible to differentiate between the two.

We're just about done implementing a Debian Repository in Azure functions. This is extremely useful to us for our low-volume repositories for distributing our training content. It works great on the adding of new deb files, since all we need to do is drop it in a folder and all the needed meta-data is automatically updated.

However, we currently have to manually remove data from our Azure Functions since there is no trigger on a file deletion. This is not ideal, and we'd really like it to be automatic. I've got to think there are a lot more use cases where triggers on deletions would also be very useful.

We also have other ideas to use Azure Functions to help monitor and keep track of change management for stored configuration files. However, again, tracking deletions would be a vital component of that.

#### Repro steps

1. Create a Azure Function Blog Trigger or Storage Queue Trigger on a given path.
2. Delete a file in that path.

NOTE: You do not receive any type of trigger or notification.

#### Expected behavior

There is a way to cause a trigger when a file is deleted.

#### Actual behavior

No notification is received when a file is deleted.

#### Known workarounds

Scan the entire file system periodically. This is not actually practical with the planned number of files.

Start by reviewing issue #1611 and the existing blob trigger and Storage Queue trigger behavior described in this issue. Define how file deletion should produce a trigger or notification, including how it is distinguished from the other change types; done means a deletion on a configured path reliably invokes the trigger.

Written by the indexing model from the issue text.