Persistent freq daemon

Created by: TomTheBear

I was asked to reimplement the CPU frequency functions because they have a high latency. This is caused by forwarding all requests to the frequency daemon, even the reads. Moreover, the frequency daemon always executed exactly one operation and exited, so each request caused a few process creations. With the pull request, the daemon is started only once and the library communicates over a UNIX socket with the daemon. Moreover, all reads are performed by the library itself and only writes are forwarded to the daemon.