Fix type-delete to allow deletion by name and ID

This change addresses bug #1286314, fixing type deletion to allow
deletion by either volume type name or ID. The former implementation
only accepted the volume type ID. Help documentation is also updated
to reflect this change.

Change-Id: I0fc66b54a7bcfa4e00a4d136ac513fa40e628dd2
Closes-Bug: #1286314
DocImpact