Moving the web-interface configurations to a custom path

https://github.com/corey-hammerton/graylog2-rpms/issues/4

Files Modified:
SOURCES/sysconfig-graylog2-web-interface
SPECS/graylog2-web-interface.spec

- Installing all files under conf in SOURCE0 to
  /etc/graylog2/web-interface in SPECS/graylog2-web-interface.spec.
- Updating the %files section to track all files under
  /etc/graylog2/web-interfaces/.
- Final entry is for /opt/%{name}/*

- Setting the java propert config.file in
  SOURCES/sysconfig-graylog2-web-interface to use the configuration
  in /etc/graylog2/web-interface/