Remove unused file
Remove LEVEL_ID
Remove old adp_maze.js
Eliminate BlocklyApps.PAGE and .LEVEL (except in Turtle)

Turtle seems like it depended on those settings, but they were never
configured, so it was bugged. Will fix soon.
Update ADP level requiredBlocks format
Removed unused variable
Explicit instructions message keys
Removing the entire concept of pages
Remove unused file
(sorta) Explicit toolboxes for maze
Fix help
Move buttons to common template
Per level toolbox and starting blocks in karel
Common-ize some feedback template stuff
Commonize feedback buttons
Remove stale template comments
Remove unused menu template
Fix maze stepSpeed scales
Separate logic for continue & try-again buttons
Callbacks for attempts & continuing to next level.