Rename container commands and classes

This gives all container-level commands a consistent
category-object-action pattern:

    blobstore-container-clear
    blobstore-container-create
    blobstore-container-delete
    blobstore-container-exists
    blobstore-container-list
Merge pull request #104 from maginatics/rename-container-commands-1.5.x

Rename container commands and classes