Refactor script infrastructure for easier usage and testability:

- add script annotation for specifying default configuration for a script
- add support for this annotation in the default configurator
- rename configurator accordingly
- add default implementation of the refineConfiguration method
- make property bag class open

libraries/scripting/common/src/kotlin/script/experimental/util/propertyBag.kt

@@ -17,7 +17,7 @@ class TypedKeyDelegate<T> {
 
 fun <T> typedKey() = TypedKeyDelegate<T>()
 
-class ChainedPropertyBag private constructor(private val parent: ChainedPropertyBag?, private val data: Map<TypedKey<*>, Any?>) {
+open class ChainedPropertyBag private constructor(private val parent: ChainedPropertyBag?, private val data: Map<TypedKey<*>, Any?>) {
     constructor(parent: ChainedPropertyBag? = null, pairs: Iterable<Pair<TypedKey<*>, Any?>>) :
             this(parent, HashMap<TypedKey<*>, Any?>().also { it.putAll(pairs) })