Add script to run make targets in a recipe category

This script allows you to run make x.recipe for all recipes in a category directory.

The syntax is:

scripts/category.sh -<action> <category>

Action can be 'f', 'r', 'c', 'u', 'cr' or 'ucr'. The script does not check the action, so if more are added to make, they will automatically work.

The minus sign before the action is optional.