* Adding new mixed type of worker group with instance overrides and mixed instances policy
* moving all count and lifecycle rule parameters to top/bottom
* adding custom IAM parts
* updating doc with new options
* fixes for spot instances
awsRegion missing in example.
It's not working without it.
And added cloudProvider setting.
It's by default "aws" and not necessary at the moment. But it's to important and should be defined if default will change in the future.