Use `get_children()` method instead
Corrected error message
Support getting codes according to the current item

This will be useful for virtual resources where the code doesn't
necessarily have to be the current item's code, but some other value
calculated according to the current item.
Put project-related URL generation in a mixin

This will allow further reuse when incorporating virtual project
resources.
Added support for cross-language resources

This allows working at the project level for individual files and folders:
seeing the overall progress as well as translating and accessing the
export view.

Fixes #75.
Also account body padding as part of the sidebar height
Also set line-height
These situations are handled by the buttons themselves
Format drop-down files and directories

Fixes #80.
Don't retain the resource when the project changed
Global warming warning