05-29 System performance and stability improvements

Today there were no interesting issues, so I will keep things short.

All database and caching operations now take less than 20ms (avg: 11ms) to return a response. I also fixed the "read error on connection to 127.0.0.1:6379" exception using the things mentioned in 05-26 Read error on connection. After spending an hour tweaking the redis, php-fpm and apache, it turned out that phpredis needed an int (1) parameter instead of a boolean (true) to specify if connections should be persistent or not. Redis memory usage hovers stable at 800 Kb even after 35 min uptime. On the Raspberry Pi client side, memory fluctuates between 9 Mb and 19 Mb. I haven't identified any memory leaks yet.