- file_info class now has new methods get_non_empty_children and count_non_empty_children; added default implementation;
- all core classes extending file_info have their implementation of those methods;
- class repository_local_file used for caching get_children() results is removed;
- class repository_local rewritten to use new methods from file_info;
- added caching of retrieved modules in file_browser::get_file_info_context_module() - this query is slow and executed multiple times on big servers
* Added a comment for the BOOK_NUM_* defines.
* Fixed broken redirects in tool/importhtml/index.php
* Fixed typo in book_preload_chapters [subchpaters => subchapters]
* Fixed copy paste docblock error in tool/print/locallib.php
* Removed the .gitignore file as Eloy had previously mentioned that.
