Enhancement: add Tests for new Processing Config selection feature.

[peterVG]

See archivematica/Issues#1166 added as a feature in AM 1.12.

Feature: Select processing configuration at the start of a Transfer
Scenario: The user is about to process a Transfer in Archivematica but she wants to change the decision point settings she has been using previously by selecting an alternate processing configuration file.
Given: That the “default”, “automated” and any additional, custom processing configuration files are saved in the Archivematica Administration tab.
And: The “default” processing configuration is set as the default option.
When: She selects an alternate processing configuration file from a drop-down select box in the Transfer tab (e.g. “my_custom_processing_config_1”)
Then: The Transfer and Ingest processing will follow the decisions set out in the newly selected processing configuration file, rather than the “default” processing configuration.
And: The user will receive a pop-up notification indicating that the Transfer has started with the selected processing configuration.
And: The “default” processing configuration will be reset as the default option the next time a Transfer is started.

A secondary test for this feature:

Feature: Use custom processing configuration file in Transfer
Scenario: The user is about to process a Transfer in Archivematica but she wants to change the decision point settings she has been using previously by inserting an alternate processing configuration file she has created and downloaded using the Administration - Processing Configuration menu.
Given: That the user has downloaded the processing configuration file called "custom3" from the Administration Dashboard menu.
And: She has renamed it to "processingMCP.xml" and inserted it at the top-level of the Transfer she is going to process.
When: She selects an alternate processing configuration file from a drop-down select box in the Transfer tab (e.g. “custom1")
Then: The options in the processingMCP.xml file will take precedence and the Transfer and Ingest processing will follow the decisions set out in the "custom3" processingMCP.xml configuration file, rather than the “custom1” processing configuration settings.

[sallain]

@peterVG If you could add a test for this before the end of August that would be great!

[peterVG]

Done. PR submitted. See 3f563c1