Add zen_sort_array() and optimize debug-log widget

Add zen_sort_array() multisort function and apply to debug-log-list widget
- removed duplicate building of logfile array to save memory (used in two places: widget and init-system)
- apply maximum limit to list in widget
- add summary line to log widget
early return to avoid arrow anti-pattern
add another early return
Merge pull request #227 from ajeh/logs-widget

Add zen_sort_array() and optimize debug-log widget