Remove multiple variations of deleting blobs from BlobContainer interface

[abeyad]

Currently in the BlobContainer interface, there are three types of delete blob methods:

1. void deleteBlob(String blobName)
2. void deleteBlobs(Collection blobNames)
3. void deleteBlobsByPrefix(String blobNamePrefix)

These methods are again redundant and present confusing semantics. Having just one deleteBlob(String blobName) is the only method that can be truly atomic (can not atomically delete a collection of blobs) and it avoids complex exception handling (what do we do if some of the blobs exist, but not others?).

[tlrx]

I agree it's confusing. The deleteBlobs(Collection blobNames) can be useful for backends that support batched deletions (like Google Cloud Storage or S3) but there's still some complex exception handling to do... so +1, maybe we should move everything to deleteBlob(String blobName).

[s1monw]

so +1, maybe we should move everything to deleteBlob(String blobName).

++