gnome update to 0.75, GUI fixes for a few options

[splintermind]

• updates gnomes to the most recent release
• enables and fixes diggingInvaders
• fixes the options for dfhack.init and announcements.txt not working
• fixed missing file names from some options in the JSON export

[pjf]

I'm glad to see the diggingInvaders tweaks! I wasn't sure that they were supposed to look like. :)

[pjf]

Merging and doing the update-zipfiles-and-things-dance. :)