Update poolApp.js

When i use Giant 0.87,  
in poolApp.js : total_used has changed to total_userd_bytes,  total_space to be total_avail_bytes
    "stats": {"total_used_bytes": 15889129472, "total_bytes": 4462378086400, "total_avail_bytes": 4436766040064}}}

in aboutPools.html :
    {{stats.total_used * 1024| bytes}} used <br>on {{stats.total_space *1024| bytes}}
should to be
    {{stats.total_used_bytes | bytes}} used <br>on {{stats.total_avail_bytes | bytes}}