Theme Compatibility:

• First pass at including theme compatibility into BuddyPress.
• Introduce dependency, theme-compatibility, template-loader files into Core component.
• Add theme compatibility classes for components with direct template access.
• Move actions and filters around for improved plugin dependency.
• Remove old $bbp references.
• Turn $bp global into byref singleton, and include methods for setting up theme compatibility. (Fixes #4470.)
• Add is_buddypress() function to bp-core-template.php.
• Rename incorrectly named bp_after_theme_setup sub-action.
• See: #3741.