[test] Add a more complete test on 'gtfs2ntfs'

[woshilapin]

Create a test fixtures GTFS including:

• Creation of trip_property
• Creation of equipment
• levels
• pathways
• platform_code
• frequencies
• use of a configuration
• use a prefix

One question remain, do we need to keep the following tests (which should now all be covered by this complete fixture):

• test/fixtures/gtfs2ntfs/levels_and_pathways
• tests/fixtures/gtfs2ntfs/platforms
• tests/fixtures/gtfs2ntfs/frequencies
• tests/fixtures/gtfs2ntfs/minimal_with_config

ref: ND-963

[patochectp]

One question remain, do we need to keep the following tests (which should now all be covered by this complete fixture):

* `test/fixtures/gtfs2ntfs/levels_and_pathways`

* `tests/fixtures/gtfs2ntfs/platforms`

* `tests/fixtures/gtfs2ntfs/frequencies`

* `tests/fixtures/gtfs2ntfs/minimal_with_config`

these tests can be removed

[woshilapin]

these tests can be removed

Done in f88a103. However, I couldn't remove tests/fixtures/gtfs2ntfs/frequencies since these fixtures are also used in tests related to ODT. Maybe a future clean up could integrate ODT tests into the main GTFS test.