argon2 implementation

- memory and time params customisable as well as "difficulty", default 1 iteration, 6000KB, 3 difficulty.
- updated the noscript bash method to work with argon2
- works in webworkers or main thread, capped at 8 threads (doesn't seem to crash firefox anymore -- we could go higher)

docker-compose.yml

@@ -38,6 +38,9 @@ services:
       - BACKEND_NAME=servers
       - SERVER_PREFIX=websrv
       #- CHALLENGE_INCLUDES_IP=1
+      - POW_TIME=1
+      - POW_KB=6000
+      - POW_DIFFICULTY=3
   nginx:
     ports:
       - 81:80