sea-query 0.16.0

on Rust Cargo

[[#112]] Introduce Nullable trait to permit custom Option<T>

[[#113]] ValueType trait should have a non-panic-ing method

[[#114]] ValueType revamp

1. Remove ValueTypeDefault
2. Change type_name to return String

[[#115]] Postgres concatenate operator (||)

[[#117]] Lock support (FOR SHARE, FOR UPDATE) for SELECT statement