Added new sub-scan mode: SCAN_POLLS (used to scan sub-boards for posted polls)
Introduced a better progress indicator (similar to poll results), using the backfill() method. 2 new attr.cfg fields allow the progress indicator colors to be configured separately from poll results (though they default to the same white on magenta). This new progress indicator is used when loading msg ptrs and scanning for votes. I will be using it while performing other searches (e.g. file libraries/dirs) as well.