Remove leftover special piplinks code

This has all been replaced by mappings in data/mappings/businesslink.csv and
data/mappings/businesslink_ukwelcomes.csv. This was done in:
e88b588cc3383ca1356ff353f56d94af1b28ab02
and:
39299ffa921c18e14fe0fdd2c734053bf24c59b6
Add significant query string to fera site
Merge pull request #852 from rjc123/newmappings

Add significant query string to fera site
titles no longer required in site yaml

Transition and Bouncer currently ignore site titles, although once upon a time
they were used in the import process to relate them to their owning
organisation. We now do this with the whitehall_slug.

Instead, let's have titles only when it should be different from the
organisation title - for example when the site is about something other than
the organisation. We'll change Transition and Bouncer to use the site title or
fallback to the organisation title.

Where there is an obvious title to use instead of the organisation title (or
the title was already different), I've done so.
Rename furl => homepage_furl

This more clearly explains the purpose of it. It should be a furl which
redirects to the same page as the homepage does.
Tweak README for homepage and homepage_furl
Merge pull request #834 from alphagov/rename_and_tweak_site_yaml

Rename and tweak site yaml contents
Remove incorrect COMEAP furl
Merge pull request #851 from rjc123/newsites

Changes to BIS legacy sites configuration
Configure thepensionservice.gov.uk TLD rewrite
Merge pull request #853 from rjc123/newmappings

Configure thepensionservice.gov.uk TLD rewrite
Add www2 alias to defra site
Configure SACN on transition tool
Merge pull request #854 from rjc123/newmappings

Site configuration and reconfiguration
Change SACN Title
Merge pull request #855 from rjc123/newmappings

Change SACN Title
Add mappings for missing authority IDs on worldpay callback
Change naturalengland TNA timestamp
Merge pull request #857 from alphagov/natural-england-timestamp

Change naturalengland TNA timestamp
Add basic mapping in case lack of querystring is significant