Shiny Gadgets, improved options for non-JSON APIs

v0.3.0

• Document default options in ?googleAuthR
• Add option(googleAuthR.rawResponse) - skip API checks on response.
• Add an example Shiny app in /inst/shiny/shiny-example.R
• Add an RStudio Addin for easy authentication. Run via menu or googleAuthR:::gar_gadget()
• Move simplifyVector option to be able to be passed in generated function, defaults to getOption("googleAuthR.jsonlite.simplifyVector")
• Remove scopes option as not used.
• Added googleAuthR.verbose to control feedback. 0 = everything, 1 = debug, 2=normal, 3=important
• Make the retry kick in more often for every 5** and 429 status error
• Support non-JSON uploads (#28)
• Add option to force user consent screen on Shiny login
• Move specification of scope for gar_auth_service to param for more flexibility
• Migrated shiny functions to Shiny Modules (#27)