Editor: added "Export Global Messages to script" menu command

[ivan-mogilko]

Fixes #1854

Adds a menu command for moving deprecated GlobalMessages to script. Script contains following:

• an array of Strings, size of 500, where each element corresponds to a single global message, whether empty or assigned.
• a helper function that converts a message number to this array's index. This is done to let use legacy message numbers, where numbers >= 500 referred to global messages, while numbers < 500 referred to room messages.
• function game_start that assigns array elements.

The intent here is to provide user a simple way to:

• extract global messages from game data xml,
• keep using these either by calling provided helper function, if wanted,
• or copy/move these texts any way they'd prefer.

Attached an example of output, generated from a default 2.72 game:
GlobalMessages.zip

Example of using this generated module:

Display(GetMessageByNumber(999));

PS. Ticket mentioned this may be done in 30 mins, but i'm guilty at spending around 2 hours on this, getting confused by editor's code organization again and some strange errors coming up.... I just wanted to clear these remaining legacy project data issues within 3.*.