Template function filters should receive relevant ids

[filosofo]

In a number of template function filters, the functions receive arguments that include the relevant object's id, but they do not pass on that id to the filter.

This is a problem because:

• It's inconsistent with how most bbPress filters behave.
• It forces a filter callback to rely on global variables, which may not be correct in the context in which it's being used.
• In general, a callback should be able to distinguish among as many situations as can be specified by the filter's parent function arguments.

My patch fixes the problem in a backwards-compatible way, by adding the appropriate id to the filters.

[sambauers]

(In [2094]) Add more args to available template filters. Props filosofo, fixes #1080.