DIRECTOR: LINGO: Implement MENUREF Datum type and STUB for Menu, Menus, MenuItem and MenuItems [WIP]

[r41k0u]

This change:

• Implements the MENUREF Datum type to refere to menus and menuItems
• Implements the missing getter and setter functions for the STUB.
• Cleans up the old way of findMenuItem() (It would have required 4 overloads)
  With these changes, all the workshop movies concerning the menus and menuItems are working, except for the name of menu workshop movie.
  This is still WIP to figure out the problem with name of menu, fix it and then it would be a PR which could be merged

[rvanlaar]

Good work. I'ld like to see two changes for me to merge the PR.
Please clean up the commits:

• remove the first commit: it has changes that are made irrelevant by the second commit
• explain the why and how on the second commit

[r41k0u]

Done

[rvanlaar]

Hi @r41k0u
Yes, I see the first part, thank you. But you seem to have missed the second part.

[bluegr]

@r41k0u Please change your commit message according to our guidelines (you removed the DIRECTOR: part)