Changing theme stack function

Changed action_init_theme to theme_header because not all themes extend
Charcoal, which has action_init_theme, but all extend Theme which has
theme_header.  Also fixing some whitespace.
Changing funtion to "action_template_header_9()"
Removing priority 9 from action_update_check
Merge pull request #1 from mmynsted/master

Changing function with Stack adds to permit wider use