Smarty upgrade deprecates usage of PHP functions as modifiers

[stwalkerster]

The next major release of Smarty will deprecate usage of real PHP functions as template modifiers.

From a quick scan of our code, it seems that most of our use of modifiers is either using Smarty built-in modifiers (eg escape, default), or Smarty plugins.

One (known) exception is team/user.tpl, which uses implode. We need to:

• Double check the codebase for other instances of unregistered modifiers
• Register any unregistered modifiers properly with Smarty

In the case of implode, I think we can get away with creating a new Smarty plugin to wrap the PHP implode(...) function into a modifier.

Reproduction: Enable PHP notices in your development environment, and browse to /internal.php/team. Observe the deprecation notice in the PHP log.

Testing: Browse to any affected pages, check that the page output is unchanged, and that no deprecation notices are written to the PHP log.