add option for case-insensitive match in unpack

In my testing case, using data_files_glob: *.tif did not match image file ending with ".TIF" even though it should have - as fnmatch should be case-insensitive. I tried to change code to re.match on compiled regex.

Does this make sense @fabian.schindler or am I misunderstanding it completely? (matching file ending with .TIF on "*.tif" regex and case=false and not matching on case=true works now correctly for me.

Also exposed glob_case option as a configuration.