Support/refactor request constructor

This came out of the request refactoring #1071
In this PR I refactored the Request constructor, mostly by extracting logic into
separate functions. I also took some initiative to move general helper functions in to the helper file.

Review please: @mikeal @FredKSchott @nylen 
If you mean line 129, then no. My i probably accidentally cut that sucker out.
I putting that back though