Fixed PdJob so it sends notify::state-reasons signals.

Use the object's state-reasons property rather than keeping a copy.
Don't shadow Job 'name' property.
Don't shadow Job 'attributes' property.
Don't shadow Printer 'name' property.
Don't shadow Printer 'description' property.
Don't shadow Printer 'location' property.
Don't shadow Printer 'ieee1284-id' property.
Don't shadow Printer 'defaults' property.

Also: fix return of unsupported attributes.
Don't shadow Printer 'supported' property.
Don't shadow Printer 'state-reasons' property.
Use generated functions to read/write object properties.
One more instance to use pd_job_get_state_reasons().
Merge pull request #4 from twaugh/fix-notify-state-reasons

Fixed object property "notify" signals.