Add support for clickTrackingUrl in search results

Problem/Motivation

We should implement optional support for the clickTrackingUrl in search results to allow Funnelback to log clicks on search results.

Steps to reproduce

N/A

Proposed resolution

We could define a config setting to allow search results to show the clickTrackingUrl instead of the raw URL. This might be complicated to figure out if nodes are being rendered out using specific view modes, but there ought to be a way to make that possible.

Remaining tasks

• Add config setting to use clickTrackingUrl
• Allow search result URL to be switched out depending on the setting
• Investigate a way to provide clickTrackingUrl to node view mode if required

User interface changes

If enabled, this setting will route clicks on search results through the Funnelback server's click tracking, and return them to the page the search result will correspond to.

API changes

No API changes, but template changes may be required to handle the switched URLs.

Data model changes

An additional config option will be required, probably a boolean.