Update functions.php

Added filter and action to extend achievement admin screen with thumbnails.
Update functions.php

Added dpa prefix where missing.
Update functions.php

Renamed thumbnail header from "Featured" to "Badge".
Update functions.php

Added a comment to clarify the naming of the column.
Revert "Update functions.php"

This reverts commit ac16b94dd07f5bdb09a349e902b3e37337688f38.
Revert "Update functions.php"

This reverts commit 3b15a3b4f8a706b799c12658ec8120c02da9f597.
Revert "Update functions.php"

This reverts commit 4ac17c7d83fec0323bb6fa0d6893cc129b8a3c08.
Revert "Revert "Update functions.php""

This reverts commit e7c8ed2c5a78476dd734109fb5458acbb84de02d.
Revert "Revert "Update functions.php""

This reverts commit bd9ea5178d1d2334cbcd4f67472930c6b00497b5.
Revert "Revert "Update functions.php""

This reverts commit c69b522672faf2397a8da72e3d92a9c5002c1220.
Revert "Update functions.php"

This reverts commit ac16b94dd07f5bdb09a349e902b3e37337688f38.
Revert "Update functions.php"

This reverts commit 3b15a3b4f8a706b799c12658ec8120c02da9f597.
Revert "Update functions.php"

This reverts commit 4ac17c7d83fec0323bb6fa0d6893cc129b8a3c08.
Revert "Update functions.php"

This reverts commit 8085cf882656d27d8c39f1d489e16a0efadb2ddc.