Moves and Copy

TypeScript variables point at values managed by a garbage collector; Rust bindings own values unless the type is Copy. This theme makes moves concrete before references appear. Planned exercises: 1. choose which binding owns a String. 2. recognise a move. 3. recognise a Copy integer. 4. fill the line that avoids using a moved value. 5. fill a clone() only where an owned duplicate is intended. 6. write a function that takes ownership. 7. write a function that returns ownership. 8. translate TS object passing into Rust moves. 9. fix a use-after-move compiler error.