v0.7.0

Highlights

• UNWIND. Expand a list into rows; may start a query.
• CASE expressions. Both CASE x WHEN ... and CASE WHEN cond ... forms.
• Comments. Line (//) and block (/* ... */).
• Map projections n { .prop, key: expr }, backed by a new CypherValue::Map.

Breaking: new Clause / Expr variants and CypherValue::Map.