* Adds `indent(prefix)` to `String`
* Moves the loading of tool/doc translation into
`editor/editor_translation.{h,cpp}`
* Makes use of doc translation when generating XML class references, and
setup the translation locale based on `-l LOCALE` CLI parameter.
The XML class reference won't be translated if `-l LOCALE` parameter is
not given, or when it's `-l en`.
(cherry picked from commit c11b1850c4)
Haoyu Qiu