Added javascript to activate bootstrap tab from off-page link.

Used by post forms to link to help file for allowed bbcode.
Source of javascript: https://github.com/twbs/bootstrap/issues/2415#issuecomment-8064201
Post, edit, quickpost and signature form links to help file for allowed bbcode.

Will link if green and allowed, will not link if red and disallowed.
Merge branch 'posthelp' into slightlysome