Aggregation changes + shiny app improvements

[jbottesini]

• added a modified aggreCAT function to calculate an aggregated mean rating and uncertainty (still a work in progress)
• edited the data input file so the aggregated values are calculated there and we can use them in the shiny app
• changes to shiny app including
• • adding a toggle option for plots that have aggregated means and uncertainty (it's not very good so it helps to be able to turn it off)
• • made separate tab for the journal predictions/merit values so they are comparable and more visible
• • added spider charts for comparison of 2 papers
• • other stuff to resolve conflicts

[daaronr]

Looking good, thanks. Mentioned some tweaks and next steps in github comments and slack,