Feature request: Add url property methods to all entity models

[dpriskorn]

Hi, I rewrote LexUtils and decided to extend the WBI models instead of rolling my own. Since WBI know the baseurl etc it should be trivial to add a url property method like I did but using the values set by the user in config. See https://github.com/dpriskorn/LexUtils/commit/aa20cb24d04b0eba6dd95ef2241d7bb597d2d6f2