JdbcWriter changes

What's in this PR :

* There was 2 config keys that didn't follow the pattern `create...Table`: changed them, so that these config keys all use the same pattern
* Since create statements became configurable, insert statements had to be configurable too : no real way to be sure that someone won't want (or need) to change the tables or columns names, breaking the insert statements in the process.
* Since adding 4 config keys made this config section a bit messy, I splitted them into 2 sub  sections : one for create statements, one for insert statements.

+ One minor change to the `props` parameter of the `setUp`method : since `Config.parseMap`takes a `Map<String, ? extends Object>`, its Scala counterpart should be `Map[String, _ <: Any]`.