Initial version of the plots in one file

All plots are constructed by a single plot1.R file, last plot is also
saved to PNG. Tweaking is needed to make sure the plots match the
problem formulation exactly (fonts, sizes, etc.)

[plot1.R]
+ Code to generate the plots 1-4 for Course Project 1
Split code for plots to files, add saving to PNG
Added .gitignore file
Switched to plotting to PNG instead of copying
Added generated plots to repo