Add support for inline child rules

[bohoffi]

Currently the ruleFor function does not support inline child rules:

• using the property name overload only allows keyof T e.g. name but not address.city
• using the member expression overload only the first part of the expression will get extracted e.g. p => p.address.city will result in address

Support for inline child rules using property paths like address.city or nested member expression like p => p.address.city needs to be added.