A couple of small improvements to CraftOS

[SquidDev]

• Make window.reposition's argument validation a little more strict. Previously it would accept window.reposition(x, y, width) (no height argument), just not act upon it.
• Use select instead of table.unpack within pastebin run.
• Use parallel.waitForAny instead of waitForAll within the dance program.
• Pipe the entire help file into textutils.pagedPrint, rather than doing it line by line.
• Remove bytecode loading disabling from bios.lua. This never worked correctly, and serves little purpose as LuaJ is not vulnerable to such exploits.

I realise many of these changes are incredibly minor, and so don't really seem worth it. However, CraftOS is a great reference to link people to when they're looking for help, and so it's always good if we can show "best practices" for using CC & Lua's features.

---

If anyone else has changes that really aren't worth a separate PR, feel free to let me know/send a patch.