Enable configuration from home directory

This adds the possibility of defining multiple locations for the config-files. The given example first searches in ~/.magpie and if it doesn't find any config-files there, it searches in the default path. This enables configuration for each individual user and fixes the problem that magpie must be run as root if it was installed as root.

This (most likely?) fixes https://github.com/charlesthomas/magpie/issues/1