Convert storage of map information into lists (requires IDL 8.0+)

Convert storage of map information from individual named variables into list
(requires IDL 8.0+) to avoid excessive use of the Execute() command and the
feeling of spaghetti code.

	modified:   create_local_files/omni_assoc_catalog.pro
	modified:   create_local_files/omni_survey_postage.pro