Move BuddyPress specific code into a separate plugin.

[imath]

Here's the plugin repo: https://github.com/imath/bp-idea-stream

This plugin will remove the hooks loading the included files in previous versions of WP Idea Stream and will include their files once done.

[imath]

• [x] Move the group's template
• [x] Move the JS specific to BuddyPress Groups
• [x] Move the unit tests specific to BuddyPress integration
• [x] Move BuddyPress specific CSS