add option --subdirs-on

Add an option to specify a string that, when it occurs in
identifiers, is treated as a separator to store harvested records
in sub-directories. As discussed in #5
fix filename escaping in Windows

On Windows do not protect `:` characters from being escaped as
they are illegal.
Fix filepaths on Windows, enable specify subdir separator

Closes #5
Closes #6

Merge branch 'hotfix/1.1.4'