Calculate the notification score from reputation rather than from hive_accounts_rank_view

This uses reptracker_endpoints.get_account_reputation function, but
inlines the call.
The first reason is that the function doesn't specify reptracker_app
schema directly. Since hivemind doesn't have it in its search_path, the
call fail.
The second reason is that the calculation is modified to bring the
resulting range closer to the scores from hive_accounts_rank_view.