Alter graphs and captions to include core CPI

This commit changes the graphing code to DL and plot core CPI as well as raw CPI;
core CPI is featured more prominantly.  The caption is also updated to reflect
this change.
Refactor code and add real Income to GDP plot

This commit moves the R code to plot CPI into its own file and replaces
the GDP code with this general purpose code.  It also changes the GDP
plots to also include gross domestic income.
Add disclaimer to the beginning of each caption

Each caption now explains that the figure and commentary is automatically
generated and then has a 'teaser' that there's 'more to come...'