Split contents of 'relational' object into classes of 'relational' package
Move relational's Expr type-branches into object
Expression.scala -> Expr.scala
Move Query branches into object
Split 'sql' object into package with classes
Put sql.Query branches into object
Put sql.Expr branches into object
Fix typos
Document RangeDomain a bit
Document StringUtils
Document relational.Environment
Document relational.Expr
Document relational.Query
Document relational.Schema
Drop unused import
Document sql.Expr
Document sql.Query
Merge default write parameterization methods into defaultWriteParameterization
Document sql.WriteParameterization