doc/blob: correct some typos

* **Hello World**: Actually named `hello_blob.c` this is a very basic example of a single threaded application that

does nothing more than demonstrate the very basic API. Although Blobstore is optimized for NVMe, this example uses

a RAM disk (malloc) back-end so that it can be executed easily in any development environment. The malloc back-end

is a `bdev` module thus this example uses not on the SPDK Framework but the `bdev` layer as well.

is a `bdev` module thus this example uses not only the SPDK Framework but the `bdev` layer as well.

* **Hello NVME Blob**: `hello_nvme_blob.c` is the non-bdev version of `hello_blob.c` and simply shows how an

application can directly integrate Blobstore with the SPDK NVMe driver without using the `bdev` layer at all.

struct spdk_bs_request_set;

~~~

These requests sets are basically bookkeeping mechanisms to help Blobstore efficiently deal will related groups

These requests sets are basically bookkeeping mechanisms to help Blobstore efficiently deal with related groups

of IO. They are an internal construct only and are pre-allocated on a per channel basis (channels were discussed

earlier). They are removed from a channel associated linked list when the set (sequence or batch) is started and

then returned to the list when completed.

~~~{.sh}

struct spdk_blob

~~~

This is an in-memory data structure that contains key elements like the blob identifier, it's current state and two

This is an in-memory data structure that contains key elements like the blob identifier, its current state and two

copies of the mutable metadata for the blob; one copy is the current metadata and the other is the last copy written

to disk.