Allow array access via indices in configuration paths

[KilowattJunkie]

• Fixes #30
• Adds and modifies peek and find methods to allow indexing of ConfigList objects
• Enables nested array and object access using indices in paths: listConfig.getString("ofObject.0.byteObj.byteVal") listConfig.getString("ofArray.2.2")

References https://github.com/lightbend/config/issues/30

Please note: I haven't (and won't) sign the contributors agreement as I prefer to stay pseudonymous; I maintain a personal fork of the project, and only offer this PR in case someone wants to continue the work. Feel free to implement and/or close as needed.

[lightbend-cla-validator]

At least one commit author (noreply@kilowattjunkie.com) is not linked to a user. See https://help.github.com/en/articles/why-are-my-commits-linked-to-the-wrong-user#commits-are-not-linked-to-any-user

[lightbend-cla-validator]

At least one commit author (noreply@kilowattjunkie.com) is not linked to a user. See https://help.github.com/en/articles/why-are-my-commits-linked-to-the-wrong-user#commits-are-not-linked-to-any-user

[lightbend-cla-validator]

At least one commit author (noreply@kilowattjunkie.com) is not linked to a user. See https://help.github.com/en/articles/why-are-my-commits-linked-to-the-wrong-user#commits-are-not-linked-to-any-user

[ennru]

We do not intend to extend the functionality of "Typesafe Config" further. See https://github.com/lightbend/config#maintained-by