Allow users to set global pr settings by default

It's clear that constantly toggling some settings is annoying for users, and there are some customizations that certain users require that we don't currently offer. 

We're going to create a menu for users to indicate settings for their pull requests that will remain active for future pull request visits:

1. Ignore whitespace
2. Tab width
3. side-by-side view
4. Red-green colorblind friendly diff colors