Implement reader software to Batch Job definition lookup

[dpwrussell]

In order to support multiple readers and versions of readers, implement a mechanism of using the software and its version to determine which job definition (and thus which Docker image) is appropriate.

Could potentially be implemented as:

• A lambda function which reads some configuration file potentially partially derived from the job definitions defined in the Batch Cloudformation deployment stage
• SSM parameters (less flexible)

[dpwrussell]

While this is still desirable in the medium term (i.e. to provide the user with options to use different version of BioFormats, etc), the immediate need of synchronising the BioFormats version used in scan and extract can be solved instead by setting the versions in stone when the scan job is launched and carried forward as a parameter to the extract job executions.