refactor code to restore pester into a separate function called Restore-PSPester
update message on what to do when pester is missing
Add ability for get-psoptions to default to new-psoptions
fix an issue with publish-pstesttools when a build has not been run since build.psm1 has been imported (try to use the default options)
make start-pspester use the last build, not just use the default options
fix an issue in restore caused some files not to be removed
Update pull-request-process to clarify role/responsibility of author and reviewers based on recent feedback from team and community. Also moved it to `.github/CONTRIBUTING.md` so that all related information can be found at one place.
