Azure plugin: change filter parameters for blob protocol
Azure plugin: change filter parameters for blob protocol

Simplify the protocol filter to switch to 'http', 'https', or 'none' to
indicate the protocol to use, rather than having to pass the colon and
slashes. This means a little extra in code and conditional checks, but
makes the filter friendlier.

mrgregwaugh/windows-azure-storage,mrgregwaugh/windows-azure-storage