New Functions for JMESPath

I'd like to propose a few additional functions for inclusion in the JMESPath specification:

[https://github.com/the-g-man/jmespath-ext](https://github.com/the-g-man/jmespath-ext)

They're not complex to implement but they add a great deal of power - for instance in dealing with recursive or normalized data structures.

I've added documentation and compliance tests for each of the three functions.