Refactor SqlQuery case class as trait with companion object, so that it will be possible better check its creation. Update BatchSql, which was directly using SqlQuery at creation, replacing it by raw (string) statement, with SqlQuery created internally with checks.

```scala
import anorm.BatchSql

// Before
BatchSql(SqlQuery("SQL")) // No longer accepted (won't compile)

// Now
BatchSql("SQL")
// Simpler and safer, as SqlQuery is created&validated internally
```
frequency value typo
Merge pull request #3046 from sharpyfox/fix_akka_doc

Scala Documentation: Akka frequency value typo
Merge pull request #3027 from cchantep/anorm-sqlquery

Refactor SqlQuery case class as trait with companion object, so that it ...