Rename all script title locale references from 'desc' to 'title'

A recent commit replaced the 'desc' locale key with 'title' and 'description'. This commit will remove the old 'desc' entries and replace the remaining references to 'desc' in the code to the new 'title' key.
Also removes obsolete locale entries from scripts.en.yml for scripts that no longer exist.
Note - these (Maze Step Levels) are not custom levels, though they're not really exposed anywhere and should probably go away at some point.