convert value passed to --robot to a list of values
make get_paths_for function accepted list of robot paths
make obtain_file function aware that self.robot_path is a list now
fix use of options.robot as list of robot paths in main.py, make --search use --robot paths, improve implementation of finding of easyconfig files in installed easyconfigs paths, enhance coverage of unit tests on main.py via toy build unit test
fix defining easyconfigs_pkg_full_paths in main.py
add --ignore-dirs config option to specify directories to ignore when searching for files/dirs
use options.ignore_dirs where applicable
style cleanup in options.py
Merge pull request #786 from boegel/multiple_robot_paths

add support for specifying multiple robot paths