Unify `SimpleSql.on(args: (Any,ParameterValue)*)` to `SimpleSql.on(args:...

... (String,ParameterValue)*)`.

I think it will avoid converting anything to parameter name, arbitrarily using [Any.toString](https://github.com/playframework/playframework/blob/master/framework/src/anorm/src/main/scala/anorm/Anorm.scala#L392) (typesafe), and would avoid maintaining code that can be unified by String (which covers all cases of parameter name).

For usage of Symbol as parameter name, as direct deprecation can hardly be used there, either existing parameter names are migrated to string (trivial `'name` to "name") or existing code update `.on(...)` to `.on1(...)` to use deprecated version:

```scala
// No longer supporter: SQL("...").on('name -> "str")
SQL("...").on1('name -> "str") // deprecated version
SQL("...").on("name" -> "str") // unified version
```