Implemented config file processing

Implemented config file processing

Configuration is taken from /etc/repa.conf and ~/.repa.conf, so it's
possible to specify system defaults in /etc/repa.conf and user-related
configuration options in ~/.repa.conf. ~/.repa.conf has higher priority
and any option from /etc/repa.conf can be reset in ~/.repa.conf

Configuration processing is implemented in a way that default values for
command line parameters are taken from configuration file(s).

Configuration section to use can be specified in command line too.

Fixes: #1141

Change-Id: I632f22674c282021983bc6a496ef1fccc0da3137
Signed-off-by: Ed Bartosh <eduard.bartosh@intel.com>
Reviewed-on: https://otctools.jf.intel.com/review/5839
Tested-by: OTC Tools Tester <ed.bartosh@linux.intel.com>
Reviewed-by: Hasan Wan <hasan.wan@intel.com>