Added support for messages (e.g., instructions).
Merge remote-tracking branch 'origin/master' into back-end-working
Improved error handling and reporting.
Implemented APIEntry.update(); moved dictionary_query.php?word=* to entry_find.php?query=* (for consistency with user_find.php?query=*).
Implemented list/update (for list_name).
Improved list handling within courses.
Implemented update() for lists, courses, units, and tests.
Finished moving dictionary_query.php to entry_find.php.
Fix for issue #19 (errors for empty lists)
Merge branch 'back-end-working' of https://github.com/lexloren/E99-Language-Learning into back-end-working
Preemptively fixed an error introduced by a recent commit (viz., by implementing copy_for_user()).
Dictionary::select_entry() => Dictionary::select_entry_by_id() (for consistency).
Implemented revert().
Trivial stylistic changes (indentation and capitalization).
Implemented timeframes.
Finished implementation.
Support for issue #21 and more unit-test updates to increase coverage.
Increase test coverage for practice apis.
Merge remote-tracking branch 'origin/master' into back-end-working
Improved error handling and reporting.