STYLE: Simplify parameter passing
STYLE: Simplify parameter passing

Refactor the logic in Slicerappstore_IndexController::categoriesAction
to simplify mapping parameter names as received from the caller to their
names as they are passed to Slicerpackages_ExtensionModel, allowing us
to remove the special-case ternary where specifying the param array key.

Also remove remaining superfluous uses of '$avalue' lambda.

midasplatform/slicerappstore,midasplatform/slicerappstore,midasplatform/slicerappstore