Issues with bu_navigation_list_pages

[mgburns]

Logic errors in the bu_navigation_list_pages function are leading to unexpected behavior when using the "page_id" and "sections" arguments.

Example bug with "sections":

Given the following page tree:

• Parent (ID=1)
  • Child (ID=2)
    • Grandchild 1 (ID=3)
    • Grandchild 2 (ID=4)

Calling bu_navigation_list_pages( array( 'sections' => array( 2, 1 ) ) should list all pages, but does not due to the ordering of the section post IDs.

Example bug with "page_id":

Given the same tree, calling bu_navigation_list_pages( array( 'page_id' => 3 ) ) will list ALL pages.

Somewhat related -- there is content navigation widget-specific logic tied up in this function that doesn't belong. (e.g. the "style" and "navigate_in_section" arguments). Cleanup would be nice.