Link check 1.8

Link check v1.8 changes:

Fixed link information showing in email.

Link check v1.7 changes:

Now using finder for performing database queries.

Link check v1.6 changes:

Now works with XF v2.0 and v2.1.

Link check v1.5 changes:

Added PHP directives.

Link check v1.4 changes:

Added 'Follow redirects' to options page. Also updated cURL code to help prevent false positives.

Link check v1.3 changes:

Fixed email subject phrasing.

Link check v1.2 changes:

Updated PHP file.

Link check v1.1 changes:

Updated addon.json file.