Refactor IrodsStatisticsAjaxView and related JQuery

[mikkonie]

Yay, found more yak shaving when fixing #1886. Certain things seem to require refactoring in the class and its usage:

• We return a list instead of a dict based on the iRODS path. The latter would make it much simpler to handle the data in JQuery instead of needlessly iterating through a list
• coll_objects term should be renamed. What even is that
• Same with data for return data within the view
• We set data-stats-url in template, but always just use the path substring from the URL. Should probably just use the iRODS path instead. I guess this is residue from the old implementation which mostly used get()
• We should query once per project and have the project UUID in stats
• ..come to think of it, is get() even used anymore? Yes, by the Vue app
• 403 and 500 statuses is not handled in the JQuery
• Unnecessary break structures in view
• stats unnecessarily returned in Ajax view even with non-200 status (it never gets used)
• HTTP status fields are returned as strings instead of integers for some weird reason
• POST tests for the view contain the md5 attribute even though it's no longer used
• Taskflow and regular view tests are in the same test_views module, that isn't according to conventions

Tasks

• [x] Return dict instead of path from view, update usage
• [x] Rename odd variables
• [x] Use data-stats-path instead of URL
• [x] Group queries per project
• [x] Verify get() usage, remove if no longer needed
• [x] Handle 403 and 500 status
• [x] Fix break spaghetti
• [x] Remove unnecessary stats
• [x] Return HTTP status as int instead of string
• [x] Update tests

[mikkonie]

Done.