Fix a bug; add new features

* Implement BApplication::formLayout static methods
* Add BeQt::OSType::UnixOS enum member
* Add method to determine executable file target platform
* Add BGuiTools namespace
* Add methods for removing rows from QFormLayout
* Add BeQt::startProcessDetached function
* Add textChanged signal to BCodeEdit and BAbstractCodeEditorDocument
* Add sleep, usleep and msleep functions for blocking waiting