Remove LocalAsyncBlobStore.

Requests from LocalBlobStore were being forwarded to
LocalAsyncBlobStore. Since the async blobstore is going to be removed, this
commit removes the LocalAsyncBlobStore and the corresponding
LocalAsyncBlobStore <-> LocalBlobStore binding. It ports the
functionality from LocalAsyncBlobStore to LocalBlobStore.

Verified that unit tests for the transient blobstore, filesystem blobstore,
swift, atmos and s3 complete successfully.

The main changes are in *ContextModule.java and BinderUtils.java for
the bindings. The other big change is in LocalBlobStore.java. Other
files have no functional changes.

Also, this will have to be rebased if pull request #126 [1] goes in
before this.

[1] https://github.com/jclouds/jclouds/pull/126
`immediateFuture` null?