Chapter links are compiled incorrectly if the course has a subdirectory above the module directories

[markkuriekkinen]

Course directory structure:

mycourse/
|-- _content
   |-- module01
   |-- module02

Usually, the module directories are directly in the root of the course repository.

Links from chapter to another chapter are broken in the above course structure.

• This regular expression does not match the chapter file path: https://github.com/apluslms/a-plus-rst-tools/blob/5354ba6c0f5eedb6f000ef6f9f0109492d463fdb/lib/html_tools.py#L128
• The regex is defined here: https://github.com/apluslms/a-plus-rst-tools/blob/5354ba6c0f5eedb6f000ef6f9f0109492d463fdb/lib/html_tools.py#L72
• The regex requires that the module directory is right under the course root (note the ^).
• In addition, the regex uses incorrect module directory names. The names contain the parent directory too in the form _content_module01. That does not match real file paths.