Brings HeartBeat Activity check in templates

i edited the required files to make new HeartBeat feature works in templates. Unlike BuddyPress legacy, the activity li element are named "bp-activity-id" so i have also included a fix in the load more functionnality so that just posted activities are not duplicated. Since 2.0 the javascript specific depedencies can be added by filtering bp_core_get_js_dependencies so i have added the hoverIntent deps that was added to jquery into this filter.

Fixes #79