Operation default options, addresses #1267

[Ksauder]

Fairly simple change to the Router to allow a set of operation options to be set for every operation on the router.
#1267

• implement basic Router Ops defaults
• test to ensure the default options are used
• test to ensure settings on Operations override the Router defaults

I picked 4 options: by_alias, exclude_unset, exclude_defaults, and exclude_none since they seemed ripe for this, but this could be expanded.

I did not tackle any sort of inheritance in this PR. Adding a Router to a Router that has defaults won't cause the default options to percolate.