Rewrite table builder calls to work with the new
`TableBuilderHelper::Column#link_to` mechanism for defining the linked
column and what it points to. This takes the link out of the
`TableBuilderHelper`, and puts it into the hands of the view.

It gives us more flexibility with regards to what can be defined as a
link in our tables and what those links point to.

This will be used in a more meaningful way in the `imports#show` page to
list `NetexImport`s and provide links to both the referential associated
with a Netex import and the imported file status page from a table row.

Leverage our newly created `ReferentialLineDecorator` to render the
header links, allowing us to use them both here and in the table of
lines on the Referentials#show page.

Used the extended decoration syntax to allow us to specify the
`ReferentialLineDecorator`, otherwise Draper will infer `LineDecorator`,
which is not what we want in this case.

Refs #3479

Delete this route and associated template files. Wasn't sure if using
`exclude:` in the routes file was the best way to do this, as I'm not
sure if there are other routes we want to exclude from here also.

I visited the page because I'm migrating templates to the new table
builder helper and this one uses table builder. Upon visiting the page,
it looked pretty wonky, and after consulting with Jean-Paul and Luc, it
turns out this page isn't used any more because the table of
`Chouette::Line`s rendered there is now instead displayed on the
Referentials#show page, obviating the need for this page.

Refs #3479