Refactor configuration for modularity

- Use singleton pattern instead of static methods in Configuration so it
  can be subclassed.
- Split helper functions and module-specific settings (namely the
  default config values) into separate classes: Configuration and
  CoreConfiguration.
- Move default config values into a properties file kept in the
  resources dir.
Use new configuration pattern in blueflood-http
keep service implementations under c.r.blueflood.service namespace
Use new config pattern in blueflood-udp

For now just use the CoreConfiguration singleton. Refactor to use its
own configuration singleton in another PR.