DRY: weathermap_footer_links() duplicated across two files

[somethingwithproof]

Summary

weathermap_footer_links() is defined identically in both weathermap-cacti-plugin.php and weathermap-cacti-plugin-mgmt.php. The only difference is the mgmt version uses __() for i18n strings while the plugin version uses bare strings.

Proposed Fix

Move the function to a shared location (lib/ or setup.php), use the i18n version, and have both files call the shared function.