[AndyB] Build thread banner 1.0

Adds a build thread banner to the message user info block.
A build thread is a thread used by members to showcase a thread which they have created to showcase their favorite project build. For example a car forum might have members showcase a build thread of their favorite restored car project.
(Example of Build thread banner)

(Example of Custom user fields)

Features:
All phrases start with buildthreadbanner_ for your convenience.
Setup:
Add a Custom user field called Banner thread with a Field ID of build_thread.
How to use:
Member can go to their visitor tab and select Account details, there they will be able to add the URL to the Build thread field.