Update 00_Startup.R

[geneorama]

Update CODE/00_Startup.R to sync between evaluation and model repositories

• Adding yihui/printr to model repo, although we may not need it after separating out paper
• Checking if packages are installed before installing
• Checking versions of required packages and updating if necessary
• Updates default repository to https://cloud.r-project.org/ to avoid needing a particular mirror
• Make sure to check for the existence of a package before checking the package version (this caused an error in the past)