Create: Gravis's Flying Hotfixes

First release. Six fixes for Create Fly bugs, moved here from Create: Connected (Fly Port) so they can be installed on their own. No blocks, items, recipes or packets are added, so it can go on only the client or only the server.

Client

• Closing the game no longer writes a "Watchdog (Client shutdown from post-main)" crash report (Flywheel worker threads were never stopped; Create-Fly#357).
• A crafting blueprint facing south with a recipe in it no longer crashes everyone who looks at it ("quat" is null in BlueprintRenderer).

Server

• The Schematicannon consumes one book/clipboard per checklist, not the whole stack.
• The Schematicannon charges Farmer's Delight rich soil farmland as rich soil, not dirt.
• A Mechanical Arm no longer stalls on an inventory whose first item has no target (Create-Fly#370).
• Mechanical Arms in schematics saved with the original Create keep their targets.

Safe next to Create: Connected (Fly Port): applying a fix twice gives the same result. If a later Create Fly changes the code a fix hooks into, that fix is skipped instead of stopping the game.