[VB4] Search single forum by default

[Barry Kabam]

Each of the sub-forums on my message board is for a separate game, and has its own theme.

When users click on the 'Search' button, I want to do two things:

1) Keep the theme that they were on, rather than reverting to our main messageboard theme.

2) By default, limit the search to only the current forum, any child forums, and any parent forums.