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 branch 'multiple_robot_paths' into feature_make_dry-run_output_readable

Conflicts:
	easybuild/main.py
add det_common_path_prefix function + unit tests
add optional prefix argument to print_msg, to disable inclusion of '==' prefix in printed messages
add --search-short/-S and --dry-run-short/-D command line options
print shorter paths for search/dry-run based on robot paths, make search pick up robot paths, align output of search/dry-run, use options.search_short and options.dry_run_short
add checks for -D/--dry-run-short
add import for all in filetools.py
Merge pull request #5 from boegel/feature_make_dry-run_output_readable

add --dry-short-short/-D and --search-short-S options, clean up implementation, add unit tests