* #79 - parent-folder-name variable support
- introductions of simplistic macros / templating support
- initially only one macro supported: {:%parent-folder-name%:}
- macro expanded only for plain-text matching rules, ignored for regexp-based rules
- for children of the root folder the macro is ignored
- unit tests for the new macros.ts
- unit tests for the testable part of updated custom-sort.ts