Updated Distribution Index spec and impl.

Added distromanager.js to represent distro elements.
Moved all distro refresh code to distromanager.js.
Overhauled assetexec.js.
Overhauled handling of assetexec.js output in landing.js.
Overhauled events emitted by assetguard.js.
Improved doenload processing in assetguard.
Updated discord-rpc to v3.0.0.
Replaced westeroscraft.json with distribution.json.
Use npm in travis for windows + linux.
Remove file extension from imports.
Added liteloader + macromod + shaders to distribution.json.

.travis.yml

@@ -40,7 +40,7 @@ script:
         -v ~/.cache/electron:/root/.cache/electron \
         -v ~/.cache/electron-builder:/root/.cache/electron-builder \
         electronuserland/builder:wine \
-        /bin/bash -c "yarn --link-duplicates --pure-lockfile && yarn travislinux"
+        /bin/bash -c "node -v && npm ci && npm run travislinux"
     else
       npm run travisdarwin
     fi