Move Allen JSON sequence handling methods to AllenOnline.

After the merge of Allen!835 (merged) and Moore!609 (merged), configuration and execution of Allen from the Moore project will be completely independent of the Allen JSON configuration sequences. (It will be done entirely through Gaudi python bindings.) The JSON handling should be removed from the Moore project to the project(s) that uses it.

This MR moves the python method for finding a JSON file for a named Allen configuration and the method for parsing a list of lines from it to the AllenOnline package. They are used in the AllenOnline tests, specifically the AllenOnline.check_duplicates test.

The relocation of the python methods were motivated by the failure of the AllenOnline.check_duplicates test. The AllenOnline.check_duplicates test runs over the output of the AllenOnline.mep_passthrough test, which runs the JSON-based Allen/Dumpers/BinaryDumpers/options/allen.py. So configuration of the AllenOnline.check_duplicates should also use the JSON configuration.

Should go together with Allen!835 (merged), Moore!609 (merged), MooreAnalysis!84 (merged).