Resolve "snake case conversion of core"

Description

This applies many fixes suggested in &14 (closed) on the core namespace:

• The core namespace is now entirely in snake_case
• New() replaced by std::make_shared<> or custom make for factory functions,
• dynamicCast() replaced by std::dynamic_pointer_cast<>(),
• Most interfaces named in I* simplified
• base namespaces renamed to __ on the filesystem and simply removed for namespaces (ui::base becomes ui)
• Mass rename for layout "managers" and dialogs

Closes #1155 (closed)

How to test it?

Run SightViewer and other apps.