Create a Context Condition that detects the namespace in the PID field

[mjordan]

Migrate 7x CLAW allows us to migrate each object's PID and populate the field_pid field in the target Islandora 8 nodes. It would be useful to have a Context Condition that detected the namespace of the PID in this field. A couple of uses for this capability:

• Primarily, to allow 7.x Islandoras that currently use the "Object namespace" Condition to replicate Contexts in Islandora 8 after migrating
• Secondarily, as a potential solution to the use case "Equivalent of "namespacing" Fedora to accommodate multisites" presented in Use case: Equivalent of "namespacing" Fedora to accommodate multisites #396.

Related issue: #999.

[mjordan]

Closing since #147 has been merged.