Installing the graylog2-radio log4j and standard configs in a custom path

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

Files Modified:
SOURCES/sysconfig-graylog2-radio
SPECS/graylog2-radio.spec

- Installing the log4j configuration for the graylog2-radio
  package in /etc/graylog2/radio/log4j.xml in
  SPECS/graylog2-radio.spec
- Installing the application configuration in /etc/graylog2/radio/

- Updating the path to the log4j.configuration property in
  SOURCES/sysconfig-graylog2-radio to the new value
  /etc/graylog2/radio/log4j.xml
- Adding the variable RADIO_CONF to SOURCES/sysconfig-graylog2-radio
  to set a custom value to the radio configuration file path,
  defaulted to /etc/graylog2-radio.conf