Added ['time'] attribute to Players POI

It's nice that we can see where a player was at logout, but now we can see when that logout was.
Merge PR# 1082
Change ctime to localtime.

See discussion in #1082
Implement a UUID lookup cache, to avoid hitting the mojang server so much

The cache is a gzip'd JSON file.  Soon we will have a small script to
help manage the cache

See #1090 and #1117