ga_model(), new auth and user activity API

• Clean up error messages
• Fix anti_sampling breaking if using date formats "4daysAgo" etc.
• Removed google_analytics_meta() for ga_meta()
• Add accountId to the output of Shiny module authDropdown when viewIdOnly=FALSE
• Add quotaUser to reporting v4 API requests to avoid quota limits if several users from same ip attempt to run API calls (#235) - default is Sys.info()[["user"]] or set via options("googleAuthR.quotaUser")
• Add ga_model_* functions to use GA data (#234)
• Add ga_model_tweet to enable data viz in tweets
• Add userActivity API via gar_clientid_activity()
• Use new authentication setup via googleAuthR v1.0.0 and gargle
• Prevent use of default client id project in non-interactive scripts.
• Update docs to use clientId dimension in user activity API calls
• Update tidyr::unnest to use cols parameter (#266)
• Add ga_custom_upload_delete() - thanks @byapprov (#263)
• Fix sending in multiple segment definitions in a list (#253)
• Fix ga_segment_list() returning data if no custom segments created (#259)
• Fix ability to list multiple dimensions and segments (#279)