Level manipulation additions

[xx-shitai-xx]

Some functions to enable creation of a online in-game level editor

Closes #59 Closes #60

Adds:

level.links

• [x] for(let l of level.links) (iterable)
• [x] level.links.add("dest.nw", x, y, width, heigh, "newX", "newY")
• [x] level.links.remove(index)

    let level = findlevel('onlinestartlocal.nw');

    let links = level.links;
    links.add('dest' + i + '.nw', 0, 0, 2, 1, "playerx", "playery");

    let i = 0;
    for (let l of links) {
        sendtorc(i + ' link ' + l.newlevel);
        i++;
    }

    links.remove(0);

level.signs

• [x] for(let s of level.signs) (iterable)
• [x] level.signs.add(x, y, "text")
• [x] level.signs.remove(index)

    let level = findlevel('onlinestartlocal.nw');

    let signs = level.signs;
    signs.add(1, 2, "asd" + i);

    let i = 0;
    for (let s of signs) {
        sendtorc(i + ' sign ' + s.text);
        i++;
    }

    signs.remove(0);

level.chests

• [x] for(let c of level.chests) (iterable)
• [x] level.chests.add(x, y, itemType, signId)
• [x] level.chests.remove(index)

    let level = findlevel('onlinestartlocal.nw');

    let chests = level.chests;
    chests.add(1, 2, 11, 0);

    let i = 0;
    for (let c of chests) {
        sendtorc(i + ' chest ' + c.x + ' ' + c.y + ' type: ' + c.itemtype + ' ' + c.signid);
        i++;
    }

    chests.remove(0);

level.npcs - [ ] level.addnpc -> level.npcs.add

Fixes:

• [x] Level saving was missing save of signs, links, chests, baddies etc

Todo:

• [x] Add ability to add/remove chests
• [x] Fix broken level layer support