theme_boost: override positioning for the '<caption>' tag for theme boost

Changes are only to boost, so no need to test clean: Activity results block test: Create an activity and assign grades to a couple of students. Add the 'activity results' block and configure to point to the respective activity. View course home and confirm that the block displays the text 'The highest grade:' above the table of results, NOT below. Competencies test: Make sure competencies are enabled View the 'Competency frameworks' admin settings page Create a new framework Back on the 'Competency frameworks' settings page, confirm that the 'List of competency frameworks' string is positioned above the frameworks table (the table will contain one entry with your recently created framework) Navigate the to the 'Learning plan templates' admin setting page Create a new learning plan template Back on the 'Learning plan templates' settings page, confirm that the 'List of learning plan templates' string is positioned above the templates table (the table will contain one entry with your recently created template) Visit admin/tool/lp/plans.php?userid=2 and confirm that the 'List of learning plans' string is positioned above the table (Table might be empty, but look for the column headings) Click the 'Evidence of prior learning' link and confirm that the 'List of evidence' string is positioned above the table (Table might be empty, but look for the column headings)