Reverting removal of Setting and Settings definitions

 * Revert "Removing unused `Setting` and `Settings` form and filters" (This reverts commit 4569c9201eed69d4d1fb4fb56e741c189128c9c0.)
 * Revert "Removing unused `Setting` entity definition" (This reverts commit 0f300097c474c935a47fb70f45c7c52a58164fce.)
 * Revert "Removing unused definition class" (This reverts commit 1b6e52acb6697f1e8e7f774f27acac86edefb3fa.)