[WIP] Port to 3.1.1 (latest stable version)

[realkotob]

Most of the porting is complete and the game starts, here are some notes on what's left.

Fixes #107

Breaking issues:

• The map is completely dark and I'm not sure why, all the objects are there and the player can move and grab and fight, but the map itself is not visible at all. Could it be a FOV issue?

• I had to redo the dungeon tileset manually because the file wasn't being loaded, so as a result the tile ids will no longer match the hardcoded themes, BUT the good news is I renamed all the tiles to the format "tile_typeX" so it will be simple to rewrite the theming to go over slabX, cobble_bloodX, sandstone_wallX, etc where X is the number of such tile types from 0 to (size -1)

• The particle effects need to be redone because of the new particle system. I can do this easily by opening the 2.1 version and working side by side.

Minor issues/notes:

• I need to re-attach all the normal maps to the tiles again.

• There was a line of gdscript that had an error: var days_into_phase = ((ages[(year + 1) % 19] + ((day + offsets[month-1]) % 30) + (int(year < 1900))) % 30) because year<1900 does not parse to an integer, did you mean that the value should be 1 if true and 0 if false? For now I forced it to an int using int( year < 1900) but not sure if that's the same result

• In the game save/loading section I had to change a json call to use the new JSON.print to convert an object to a string, but the line data.parse_json(file.get_line()) in restore_game I wasn't sure how to convert because I'm not sure what it does or whether it's still working 😆

• I renamed all usages of owner to parent since "owner" is a reserved property in godot 3 (it refers to the instanced node that this node was loaded with). It might make less sense but it can be changed if desired to something like "ob_owner". Similary I changed name to ob_name since "name" is reserved for all nodes now, as a result some of the exported name properties will need to to be set again manually.

• The buttons in the title screen aren't being selected properly, for now I just made it start a new game after running the game.

[realkotob]

There are some changes I didn't mention and I'm sure more issues will pop up, but this is looking great already (except for the part where everything is dark lol)

[cyberfilth]

Casting year < 1900 to an Integer is absolutely fine and is probably something that I should have done originally.
Also, it looks like the months array in the same function never ended up being used, so that can be removed.

I've set up a new 3.1port branch to merge the changes into.

[realkotob]

@cyberfilth This is great, I'll send the next PRs to the new 3.1 port branch.

Next I'll be working on the main breaking issue of not being able to see the game, since I can't really work with the themes or particle effects if I can't see them :b (and those 2 changes are more straightforward)

I probably won't have time during the week to fix it but you should expect to hear from me next weekend.