Implement Vanilla Mode And Tools to Change

[brodieG]

In order to comply with CRAN requirements, this package will default to not doing any of the things that could cause concerns (e.g. search path manip, etc). So need to:

• Change default state management options
• Add warning encouraging people to switch to "Spice"(?) mode
• Add function to do the above, which would propose a diff to existing .Rprofile or similar files and let the user accept/reject